| Message ID | 20201026083401.13231-9-mark.cave-ayland@ilande.co.uk |
|---|---|
| State | New |
| Headers | show |
| Series | dev-serial: minor fixes and improvements | expand |
Hello, (Cc-ing Aurelien who introduced the support for modem control, and Jason who added the missing THRE and TEMT flags). Mark Cave-Ayland, le lun. 26 oct. 2020 08:34:00 +0000, a ecrit: > The FTDI_GET_MDM_ST response should only return a single byte indicating the > modem status with bit 0 cleared (as documented in the Linux ftdi_sio.h header > file). > > Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk> > --- > hw/usb/dev-serial.c | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/hw/usb/dev-serial.c b/hw/usb/dev-serial.c > index 4c374d0790..fa734bcf54 100644 > --- a/hw/usb/dev-serial.c > +++ b/hw/usb/dev-serial.c > @@ -360,9 +360,8 @@ static void usb_serial_handle_control(USBDevice *dev, USBPacket *p, > /* TODO: TX ON/OFF */ > break; > case VendorDeviceRequest | FTDI_GET_MDM_ST: > - data[0] = usb_get_modem_lines(s) | 1; > - data[1] = FTDI_THRE | FTDI_TEMT; > - p->actual_length = 2; > + data[0] = usb_get_modem_lines(s); > + p->actual_length = 1; Err, but Linux' drivers/usb/serial/ftdi_sio.c:ftdi_process_packet() contradicts this: if (len < 2) { dev_dbg(&port->dev, "malformed packet\n"); return 0; } status = buf[0] & FTDI_STATUS_B0_MASK; if (status != priv->prev_status) { char diff_status = status ^ priv->prev_status; if (diff_status & FTDI_RS0_CTS) port->icount.cts++; [...] /* save if the transmitter is empty or not */ if (buf[1] & FTDI_RS_TEMT) priv->transmit_empty = 1; else priv->transmit_empty = 0; Did you actually get an issue with seeing this packet contain two bytes? Samuel
On 26/10/2020 09:54, Samuel Thibault wrote: > Hello, > > (Cc-ing Aurelien who introduced the support for modem control, and Jason > who added the missing THRE and TEMT flags). > > Mark Cave-Ayland, le lun. 26 oct. 2020 08:34:00 +0000, a ecrit: >> The FTDI_GET_MDM_ST response should only return a single byte indicating the >> modem status with bit 0 cleared (as documented in the Linux ftdi_sio.h header >> file). >> >> Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk> >> --- >> hw/usb/dev-serial.c | 5 ++--- >> 1 file changed, 2 insertions(+), 3 deletions(-) >> >> diff --git a/hw/usb/dev-serial.c b/hw/usb/dev-serial.c >> index 4c374d0790..fa734bcf54 100644 >> --- a/hw/usb/dev-serial.c >> +++ b/hw/usb/dev-serial.c >> @@ -360,9 +360,8 @@ static void usb_serial_handle_control(USBDevice *dev, USBPacket *p, >> /* TODO: TX ON/OFF */ >> break; >> case VendorDeviceRequest | FTDI_GET_MDM_ST: >> - data[0] = usb_get_modem_lines(s) | 1; >> - data[1] = FTDI_THRE | FTDI_TEMT; >> - p->actual_length = 2; >> + data[0] = usb_get_modem_lines(s); >> + p->actual_length = 1; > > Err, but Linux' drivers/usb/serial/ftdi_sio.c:ftdi_process_packet() > contradicts this: > > if (len < 2) { > dev_dbg(&port->dev, "malformed packet\n"); > return 0; > } > > status = buf[0] & FTDI_STATUS_B0_MASK; > if (status != priv->prev_status) { > char diff_status = status ^ priv->prev_status; > > if (diff_status & FTDI_RS0_CTS) > port->icount.cts++; > > [...] > > /* save if the transmitter is empty or not */ > if (buf[1] & FTDI_RS_TEMT) > priv->transmit_empty = 1; > else > priv->transmit_empty = 0; > > Did you actually get an issue with seeing this packet contain two bytes? Hi Samuel, Thanks for the review! There are 2 different places where the status is read: the one above in ftdi_process_packet() relates to the control packet header for incoming data which is always 2 bytes, whereas this relates to FTDI_SIO_GET_MODEM_STATUS_REQUEST in https://elixir.bootlin.com/linux/latest/source/drivers/usb/serial/ftdi_sio.c#L2825. I have a FTDI Chipi-X adapter to compare with and that returns 2 bytes, but it looks like I mis-read the code and it's the SIO chipsets that return 1 byte which are older than the chipset being emulated by QEMU. This came from reading https://elixir.bootlin.com/linux/latest/source/drivers/usb/serial/ftdi_sio.h#L415 which states that only 1 byte should be returned, but of course that comment could be out of date. A quick test shows my Chipi-X returns 0x1 0x60 with nothing attached in response to FTDI_SIO_GET_MODEM_STATUS_REQUEST: assuming the reply length should be 2 bytes, the comment about B0-B3 being zero and the response from my Chip-X above suggests that the "| 1" should still be dropped from the response. ATB, Mark.
Mark Cave-Ayland, le lun. 26 oct. 2020 10:58:43 +0000, a ecrit: > On 26/10/2020 09:54, Samuel Thibault wrote: > > Mark Cave-Ayland, le lun. 26 oct. 2020 08:34:00 +0000, a ecrit: > > > The FTDI_GET_MDM_ST response should only return a single byte indicating the > > > modem status with bit 0 cleared (as documented in the Linux ftdi_sio.h header > > > file). > > > > > > Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk> > > > --- > > > hw/usb/dev-serial.c | 5 ++--- > > > 1 file changed, 2 insertions(+), 3 deletions(-) > > > > > > diff --git a/hw/usb/dev-serial.c b/hw/usb/dev-serial.c > > > index 4c374d0790..fa734bcf54 100644 > > > --- a/hw/usb/dev-serial.c > > > +++ b/hw/usb/dev-serial.c > > > @@ -360,9 +360,8 @@ static void usb_serial_handle_control(USBDevice *dev, USBPacket *p, > > > /* TODO: TX ON/OFF */ > > > break; > > > case VendorDeviceRequest | FTDI_GET_MDM_ST: > > > - data[0] = usb_get_modem_lines(s) | 1; > > > - data[1] = FTDI_THRE | FTDI_TEMT; > > > - p->actual_length = 2; > > > + data[0] = usb_get_modem_lines(s); > > > + p->actual_length = 1; > > [...] > A quick test shows my Chipi-X returns 0x1 0x60 with nothing attached in > response to FTDI_SIO_GET_MODEM_STATUS_REQUEST: assuming the reply length > should be 2 bytes, the comment about B0-B3 being zero and the response from > my Chip-X above suggests that the "| 1" should still be dropped from the > response. Aurelien, you introduced the "| 1" in commit abb8a13918ecc1e8160aa78582de9d5224ea70df Author: Aurelien Jarno <aurelien@aurel32.net> Date: Wed Aug 13 04:23:17 2008 +0000 usb-serial: add support for modem lines [...] @@ -357,9 +393,9 @@ static int usb_serial_handle_control(USBDevice *dev, int request, int value, /* TODO: TX ON/OFF */ break; case DeviceInVendor | FTDI_GET_MDM_ST: - /* TODO: return modem status */ - data[0] = 0; - ret = 1; + data[0] = usb_get_modem_lines(s) | 1; + data[1] = 0; + ret = 2; break; do you know exactly what it is for? Samuel
On Mon, Oct 26, 2020 at 7:21 AM Samuel Thibault <samuel.thibault@gnu.org> wrote: > > Mark Cave-Ayland, le lun. 26 oct. 2020 10:58:43 +0000, a ecrit: > > On 26/10/2020 09:54, Samuel Thibault wrote: > > > Mark Cave-Ayland, le lun. 26 oct. 2020 08:34:00 +0000, a ecrit: > > > > The FTDI_GET_MDM_ST response should only return a single byte indicating the > > > > modem status with bit 0 cleared (as documented in the Linux ftdi_sio.h header > > > > file). > > > > > > > > Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk> > > > > --- > > > > hw/usb/dev-serial.c | 5 ++--- > > > > 1 file changed, 2 insertions(+), 3 deletions(-) > > > > > > > > diff --git a/hw/usb/dev-serial.c b/hw/usb/dev-serial.c > > > > index 4c374d0790..fa734bcf54 100644 > > > > --- a/hw/usb/dev-serial.c > > > > +++ b/hw/usb/dev-serial.c > > > > @@ -360,9 +360,8 @@ static void usb_serial_handle_control(USBDevice *dev, USBPacket *p, > > > > /* TODO: TX ON/OFF */ > > > > break; > > > > case VendorDeviceRequest | FTDI_GET_MDM_ST: > > > > - data[0] = usb_get_modem_lines(s) | 1; > > > > - data[1] = FTDI_THRE | FTDI_TEMT; > > > > - p->actual_length = 2; > > > > + data[0] = usb_get_modem_lines(s); > > > > + p->actual_length = 1; > > > > [...] > > A quick test shows my Chipi-X returns 0x1 0x60 with nothing attached in > > response to FTDI_SIO_GET_MODEM_STATUS_REQUEST: assuming the reply length > > should be 2 bytes, the comment about B0-B3 being zero and the response from > > my Chip-X above suggests that the "| 1" should still be dropped from the > > response. > > Aurelien, you introduced the "| 1" in > > commit abb8a13918ecc1e8160aa78582de9d5224ea70df > Author: Aurelien Jarno <aurelien@aurel32.net> > Date: Wed Aug 13 04:23:17 2008 +0000 > > usb-serial: add support for modem lines > > [...] > @@ -357,9 +393,9 @@ static int usb_serial_handle_control(USBDevice *dev, int request, int value, > /* TODO: TX ON/OFF */ > break; > case DeviceInVendor | FTDI_GET_MDM_ST: > - /* TODO: return modem status */ > - data[0] = 0; > - ret = 1; > + data[0] = usb_get_modem_lines(s) | 1; > + data[1] = 0; > + ret = 2; > break; > > do you know exactly what it is for? Hi, I'm not particularly familiar with the FTDI USB serial devices. I found setting FTDI_THRE | FTDI_TEMT by comparing with real hardware. A little searching found this: https://elixir.bootlin.com/linux/latest/source/drivers/usb/serial/ftdi_sio.h#L541 That shows "B0 Reserved - must be 1", so maybe that is why "| 1" was added? Regards, Jason
On 26/10/2020 13:00, Jason Andryuk wrote: > On Mon, Oct 26, 2020 at 7:21 AM Samuel Thibault <samuel.thibault@gnu.org> wrote: >> >> Mark Cave-Ayland, le lun. 26 oct. 2020 10:58:43 +0000, a ecrit: >>> On 26/10/2020 09:54, Samuel Thibault wrote: >>>> Mark Cave-Ayland, le lun. 26 oct. 2020 08:34:00 +0000, a ecrit: >>>>> The FTDI_GET_MDM_ST response should only return a single byte indicating the >>>>> modem status with bit 0 cleared (as documented in the Linux ftdi_sio.h header >>>>> file). >>>>> >>>>> Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk> >>>>> --- >>>>> hw/usb/dev-serial.c | 5 ++--- >>>>> 1 file changed, 2 insertions(+), 3 deletions(-) >>>>> >>>>> diff --git a/hw/usb/dev-serial.c b/hw/usb/dev-serial.c >>>>> index 4c374d0790..fa734bcf54 100644 >>>>> --- a/hw/usb/dev-serial.c >>>>> +++ b/hw/usb/dev-serial.c >>>>> @@ -360,9 +360,8 @@ static void usb_serial_handle_control(USBDevice *dev, USBPacket *p, >>>>> /* TODO: TX ON/OFF */ >>>>> break; >>>>> case VendorDeviceRequest | FTDI_GET_MDM_ST: >>>>> - data[0] = usb_get_modem_lines(s) | 1; >>>>> - data[1] = FTDI_THRE | FTDI_TEMT; >>>>> - p->actual_length = 2; >>>>> + data[0] = usb_get_modem_lines(s); >>>>> + p->actual_length = 1; >>>> >> [...] >>> A quick test shows my Chipi-X returns 0x1 0x60 with nothing attached in >>> response to FTDI_SIO_GET_MODEM_STATUS_REQUEST: assuming the reply length >>> should be 2 bytes, the comment about B0-B3 being zero and the response from >>> my Chip-X above suggests that the "| 1" should still be dropped from the >>> response. >> >> Aurelien, you introduced the "| 1" in >> >> commit abb8a13918ecc1e8160aa78582de9d5224ea70df >> Author: Aurelien Jarno <aurelien@aurel32.net> >> Date: Wed Aug 13 04:23:17 2008 +0000 >> >> usb-serial: add support for modem lines >> >> [...] >> @@ -357,9 +393,9 @@ static int usb_serial_handle_control(USBDevice *dev, int request, int value, >> /* TODO: TX ON/OFF */ >> break; >> case DeviceInVendor | FTDI_GET_MDM_ST: >> - /* TODO: return modem status */ >> - data[0] = 0; >> - ret = 1; >> + data[0] = usb_get_modem_lines(s) | 1; >> + data[1] = 0; >> + ret = 2; >> break; >> >> do you know exactly what it is for? > > Hi, > > I'm not particularly familiar with the FTDI USB serial devices. I > found setting FTDI_THRE | FTDI_TEMT by comparing with real hardware. > > A little searching found this: > https://elixir.bootlin.com/linux/latest/source/drivers/usb/serial/ftdi_sio.h#L541 > > That shows "B0 Reserved - must be 1", so maybe that is why "| 1" was added? Right - that's for the modem status returned as part of the first 2 status bytes for incoming data which is slightly different from modem status returned directly from FTDI_SIO_GET_MODEM_STATUS: https://elixir.bootlin.com/linux/latest/source/drivers/usb/serial/ftdi_sio.h#L423. It is the latter which this patch changes and appears to match what I see on my Chipi-X hardware here. ATB, Mark.
On Mon, Oct 26, 2020 at 9:40 AM Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk> wrote: > > On 26/10/2020 13:00, Jason Andryuk wrote: > > > On Mon, Oct 26, 2020 at 7:21 AM Samuel Thibault <samuel.thibault@gnu.org> wrote: > >> > >> Mark Cave-Ayland, le lun. 26 oct. 2020 10:58:43 +0000, a ecrit: > >>> On 26/10/2020 09:54, Samuel Thibault wrote: > >>>> Mark Cave-Ayland, le lun. 26 oct. 2020 08:34:00 +0000, a ecrit: > >>>>> The FTDI_GET_MDM_ST response should only return a single byte indicating the > >>>>> modem status with bit 0 cleared (as documented in the Linux ftdi_sio.h header > >>>>> file). > >>>>> > >>>>> Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk> > >>>>> --- > >>>>> hw/usb/dev-serial.c | 5 ++--- > >>>>> 1 file changed, 2 insertions(+), 3 deletions(-) > >>>>> > >>>>> diff --git a/hw/usb/dev-serial.c b/hw/usb/dev-serial.c > >>>>> index 4c374d0790..fa734bcf54 100644 > >>>>> --- a/hw/usb/dev-serial.c > >>>>> +++ b/hw/usb/dev-serial.c > >>>>> @@ -360,9 +360,8 @@ static void usb_serial_handle_control(USBDevice *dev, USBPacket *p, > >>>>> /* TODO: TX ON/OFF */ > >>>>> break; > >>>>> case VendorDeviceRequest | FTDI_GET_MDM_ST: > >>>>> - data[0] = usb_get_modem_lines(s) | 1; > >>>>> - data[1] = FTDI_THRE | FTDI_TEMT; > >>>>> - p->actual_length = 2; > >>>>> + data[0] = usb_get_modem_lines(s); > >>>>> + p->actual_length = 1; > >>>> > >> [...] > >>> A quick test shows my Chipi-X returns 0x1 0x60 with nothing attached in > >>> response to FTDI_SIO_GET_MODEM_STATUS_REQUEST: assuming the reply length > >>> should be 2 bytes, the comment about B0-B3 being zero and the response from > >>> my Chip-X above suggests that the "| 1" should still be dropped from the > >>> response. > >> > >> Aurelien, you introduced the "| 1" in > >> > >> commit abb8a13918ecc1e8160aa78582de9d5224ea70df > >> Author: Aurelien Jarno <aurelien@aurel32.net> > >> Date: Wed Aug 13 04:23:17 2008 +0000 > >> > >> usb-serial: add support for modem lines > >> > >> [...] > >> @@ -357,9 +393,9 @@ static int usb_serial_handle_control(USBDevice *dev, int request, int value, > >> /* TODO: TX ON/OFF */ > >> break; > >> case DeviceInVendor | FTDI_GET_MDM_ST: > >> - /* TODO: return modem status */ > >> - data[0] = 0; > >> - ret = 1; > >> + data[0] = usb_get_modem_lines(s) | 1; > >> + data[1] = 0; > >> + ret = 2; > >> break; > >> > >> do you know exactly what it is for? > > > > Hi, > > > > I'm not particularly familiar with the FTDI USB serial devices. I > > found setting FTDI_THRE | FTDI_TEMT by comparing with real hardware. > > > > A little searching found this: > > https://elixir.bootlin.com/linux/latest/source/drivers/usb/serial/ftdi_sio.h#L541 > > > > That shows "B0 Reserved - must be 1", so maybe that is why "| 1" was added? > > Right - that's for the modem status returned as part of the first 2 status bytes for > incoming data which is slightly different from modem status returned directly from > FTDI_SIO_GET_MODEM_STATUS: > https://elixir.bootlin.com/linux/latest/source/drivers/usb/serial/ftdi_sio.h#L423. Okay, sorry for the confusion there. I thought your "it's the SIO chipsets that return 1 byte which are older than the chipset being emulated by QEMU" meant you thought your change to 1 byte was unnecessary. You also posted two bytes (0x1 0x60) from your hardware. > It is the latter which this patch changes and appears to match what I see on my > Chipi-X hardware here. I don't have my hardware readily available, but I must have been seeing 2 bytes from FTDI_GET_MDM_ST with data[1] = FTDI_THRE | FTDI_TEMT; to make the change. I don't have the USB captures anymore to compare the lowest bit value. So right now you are just interested in dropping the lowest bit setting but preserving the 2 bytes modem status? Regards, Jason
Mark Cave-Ayland, le lun. 26 oct. 2020 13:40:05 +0000, a ecrit: > On 26/10/2020 13:00, Jason Andryuk wrote: > > On Mon, Oct 26, 2020 at 7:21 AM Samuel Thibault <samuel.thibault@gnu.org> wrote: > > > Aurelien, you introduced the "| 1" in > > > > > > commit abb8a13918ecc1e8160aa78582de9d5224ea70df > > > Author: Aurelien Jarno <aurelien@aurel32.net> > > > Date: Wed Aug 13 04:23:17 2008 +0000 > > > > > > usb-serial: add support for modem lines > > > > > > [...] > > > @@ -357,9 +393,9 @@ static int usb_serial_handle_control(USBDevice *dev, int request, int value, > > > /* TODO: TX ON/OFF */ > > > break; > > > case DeviceInVendor | FTDI_GET_MDM_ST: > > > - /* TODO: return modem status */ > > > - data[0] = 0; > > > - ret = 1; > > > + data[0] = usb_get_modem_lines(s) | 1; > > > + data[1] = 0; > > > + ret = 2; > > > break; > > > > I'm not particularly familiar with the FTDI USB serial devices. I > > found setting FTDI_THRE | FTDI_TEMT by comparing with real hardware. > > > > A little searching found this: > > https://elixir.bootlin.com/linux/latest/source/drivers/usb/serial/ftdi_sio.h#L541 > > > > That shows "B0 Reserved - must be 1", so maybe that is why "| 1" was added? > > Right - that's for the modem status returned as part of the first 2 status > bytes for incoming data which is slightly different from modem status > returned directly from FTDI_SIO_GET_MODEM_STATUS: https://elixir.bootlin.com/linux/latest/source/drivers/usb/serial/ftdi_sio.h#L423. > > It is the latter which this patch changes and appears to match what I see on > my Chipi-X hardware here. Aurelien, do you remember the reason for the addition of 1 here? It does look like the confusion between the incoming data bytes and the modem status bytes. Samuel
On 26/10/2020 15:04, Samuel Thibault wrote: > Mark Cave-Ayland, le lun. 26 oct. 2020 13:40:05 +0000, a ecrit: >> On 26/10/2020 13:00, Jason Andryuk wrote: >>> On Mon, Oct 26, 2020 at 7:21 AM Samuel Thibault <samuel.thibault@gnu.org> wrote: >>>> Aurelien, you introduced the "| 1" in >>>> >>>> commit abb8a13918ecc1e8160aa78582de9d5224ea70df >>>> Author: Aurelien Jarno <aurelien@aurel32.net> >>>> Date: Wed Aug 13 04:23:17 2008 +0000 >>>> >>>> usb-serial: add support for modem lines >>>> >>>> [...] >>>> @@ -357,9 +393,9 @@ static int usb_serial_handle_control(USBDevice *dev, int request, int value, >>>> /* TODO: TX ON/OFF */ >>>> break; >>>> case DeviceInVendor | FTDI_GET_MDM_ST: >>>> - /* TODO: return modem status */ >>>> - data[0] = 0; >>>> - ret = 1; >>>> + data[0] = usb_get_modem_lines(s) | 1; >>>> + data[1] = 0; >>>> + ret = 2; >>>> break; >>> >>> I'm not particularly familiar with the FTDI USB serial devices. I >>> found setting FTDI_THRE | FTDI_TEMT by comparing with real hardware. >>> >>> A little searching found this: >>> https://elixir.bootlin.com/linux/latest/source/drivers/usb/serial/ftdi_sio.h#L541 >>> >>> That shows "B0 Reserved - must be 1", so maybe that is why "| 1" was added? >> >> Right - that's for the modem status returned as part of the first 2 status >> bytes for incoming data which is slightly different from modem status >> returned directly from FTDI_SIO_GET_MODEM_STATUS: https://elixir.bootlin.com/linux/latest/source/drivers/usb/serial/ftdi_sio.h#L423. >> >> It is the latter which this patch changes and appears to match what I see on >> my Chipi-X hardware here. > > Aurelien, do you remember the reason for the addition of 1 here? It does > look like the confusion between the incoming data bytes and the modem > status bytes. I spent a bit of time this morning doing some further tests on Linux using 2 machines and a test program to check CTS and usbmon: usbmon when adapter unplugged: ffff95a4bf2dd300 2366831506 S Ci:4:004:0 s c0 05 0000 0000 0002 2 < ffff95a4bf2dd300 2366831607 C Ci:4:004:0 0 2 = 0160 usbmon when adapter plugged in and remote connected to minicom: ffff95a4452a79c0 2457273895 S Ci:4:004:0 s c0 05 0000 0000 0002 2 < ffff95a4452a79c0 2457274057 C Ci:4:004:0 0 2 = 3160 It seems I made a mistake here since the response is interpreted as 2 bytes rather than a single little-endian word: with CTS asserted on the remote the first byte is 0x31 == FTDI_CTS | FTDI_DSR | 1, whilst the 2nd byte is 0x60 == FTDI_THRE | FTDI_TEMT which matches the existing QEMU code rather than the comments in ftdi_sio.h. So sorry for the noise: I'll drop this patch from the series and post a v2 shortly. ATB, Mark.
On Tue, Oct 27, 2020 at 9:18 AM Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk> wrote: > > I spent a bit of time this morning doing some further tests on Linux using 2 machines > and a test program to check CTS and usbmon: > > usbmon when adapter unplugged: > ffff95a4bf2dd300 2366831506 S Ci:4:004:0 s c0 05 0000 0000 0002 2 < > ffff95a4bf2dd300 2366831607 C Ci:4:004:0 0 2 = 0160 > > usbmon when adapter plugged in and remote connected to minicom: > ffff95a4452a79c0 2457273895 S Ci:4:004:0 s c0 05 0000 0000 0002 2 < > ffff95a4452a79c0 2457274057 C Ci:4:004:0 0 2 = 3160 > > It seems I made a mistake here since the response is interpreted as 2 bytes rather > than a single little-endian word: with CTS asserted on the remote the first byte is > 0x31 == FTDI_CTS | FTDI_DSR | 1, whilst the 2nd byte is 0x60 == FTDI_THRE | FTDI_TEMT > which matches the existing QEMU code rather than the comments in ftdi_sio.h. > > So sorry for the noise: I'll drop this patch from the series and post a v2 shortly. No worries. Thanks for investigating. (I had the thought that maybe reserve bit 0 differentiates one and two byte responses? Bit 0 clear indicates a 1-byte response and set indicates a 2 bit response. But I'm just guessing.) Regards, Jason
diff --git a/hw/usb/dev-serial.c b/hw/usb/dev-serial.c index 4c374d0790..fa734bcf54 100644 --- a/hw/usb/dev-serial.c +++ b/hw/usb/dev-serial.c @@ -360,9 +360,8 @@ static void usb_serial_handle_control(USBDevice *dev, USBPacket *p, /* TODO: TX ON/OFF */ break; case VendorDeviceRequest | FTDI_GET_MDM_ST: - data[0] = usb_get_modem_lines(s) | 1; - data[1] = FTDI_THRE | FTDI_TEMT; - p->actual_length = 2; + data[0] = usb_get_modem_lines(s); + p->actual_length = 1; break; case VendorDeviceOutRequest | FTDI_SET_EVENT_CHR: /* TODO: handle it */
The FTDI_GET_MDM_ST response should only return a single byte indicating the modem status with bit 0 cleared (as documented in the Linux ftdi_sio.h header file). Signed-off-by: Mark Cave-Ayland <mark.cave-ayland@ilande.co.uk> --- hw/usb/dev-serial.c | 5 ++--- 1 file changed, 2 insertions(+), 3 deletions(-)