diff mbox series

[v4,2/2] ata: pata_falcon: add data_swab option to byte-swap disk data

Message ID 20230822221359.31024-3-schmitzmic@gmail.com
State New
Headers show
Series [v4,1/2] ata: pata_falcon: fix IO base selection for Q40 | expand

Commit Message

Michael Schmitz Aug. 22, 2023, 10:13 p.m. UTC 
Some users of pata_falcon on Q40 have IDE disks in default
IDE little endian byte order, whereas legacy disks use
host-native big-endian byte order as on the Atari Falcon.

Add module parameter 'data_swab' to allow connecting drives
with non-native data byte order. Drives selected by the
data_swap bit mask will have their user data byte-swapped to
host byte order, i.e. 'pata_falcon.data_swab=2' will byte-swap
all user data on drive B, leaving data on drive A in native
byte order. On Q40, drives on a second IDE interface may be
added to the bit mask as bits 2 and 3.

Default setting is no byte swapping, i.e. compatibility with
the native Falcon or Q40 operating system disk format.

Cc: William R Sowerbutts <will@sowerbutts.com>
Cc: Finn Thain <fthain@linux-m68k.org>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Tested-by: William R Sowerbutts <will@sowerbutts.com>
Signed-off-by: Michael Schmitz <schmitzmic@gmail.com>

---

Changes since v2:

Geert Uytterhoeven:
- only shift swap bitmask if pdev->id > 0

Finn Thain:
- use pdev->devno directly for byte swap check

Changes since v1:

Damien Le Moal:
- change patch title
- drop swap_data flag

Finn Thain:
- drop allocation of ap->private struct, use field as bitmask

Changes since RFC v4:

Geert Uytterhoeven:
- don't shift static module parameter for drive 3/4 bitmask
- simplify bit mask calculation to always use pdev->id

Finn Thain:
- correct bit numbers for drive 3/4

Changes since RFC v3:

- split off this byte swap handling into separate patch

- add hint regarding third and fourth drive on Q40

Finn Thain:
- rename module parameter to 'data_swab' to better reflect its use

William Sowerbutts:
- correct IDE drive number used in data swap conditional
---
 drivers/ata/pata_falcon.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

Comments

Geert Uytterhoeven Aug. 23, 2023, 9:10 a.m. UTC | #1 
On Wed, Aug 23, 2023 at 12:14 AM Michael Schmitz <schmitzmic@gmail.com> wrote:
> Some users of pata_falcon on Q40 have IDE disks in default
> IDE little endian byte order, whereas legacy disks use
> host-native big-endian byte order as on the Atari Falcon.
>
> Add module parameter 'data_swab' to allow connecting drives
> with non-native data byte order. Drives selected by the
> data_swap bit mask will have their user data byte-swapped to
> host byte order, i.e. 'pata_falcon.data_swab=2' will byte-swap
> all user data on drive B, leaving data on drive A in native
> byte order. On Q40, drives on a second IDE interface may be
> added to the bit mask as bits 2 and 3.
>
> Default setting is no byte swapping, i.e. compatibility with
> the native Falcon or Q40 operating system disk format.
>
> Cc: William R Sowerbutts <will@sowerbutts.com>
> Cc: Finn Thain <fthain@linux-m68k.org>
> Cc: Geert Uytterhoeven <geert@linux-m68k.org>
> Tested-by: William R Sowerbutts <will@sowerbutts.com>
> Signed-off-by: Michael Schmitz <schmitzmic@gmail.com>
>
> ---
>
> Changes since v2:
>
> Geert Uytterhoeven:
> - only shift swap bitmask if pdev->id > 0

Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>

Gr{oetje,eeting}s,

                        Geert
Geert Uytterhoeven Aug. 23, 2023, 9:10 a.m. UTC | #2 
On Wed, Aug 23, 2023 at 11:10 AM Geert Uytterhoeven
<geert@linux-m68k.org> wrote:
> On Wed, Aug 23, 2023 at 12:14 AM Michael Schmitz <schmitzmic@gmail.com> wrote:
> > Some users of pata_falcon on Q40 have IDE disks in default
> > IDE little endian byte order, whereas legacy disks use
> > host-native big-endian byte order as on the Atari Falcon.
> >
> > Add module parameter 'data_swab' to allow connecting drives
> > with non-native data byte order. Drives selected by the
> > data_swap bit mask will have their user data byte-swapped to
> > host byte order, i.e. 'pata_falcon.data_swab=2' will byte-swap
> > all user data on drive B, leaving data on drive A in native
> > byte order. On Q40, drives on a second IDE interface may be
> > added to the bit mask as bits 2 and 3.
> >
> > Default setting is no byte swapping, i.e. compatibility with
> > the native Falcon or Q40 operating system disk format.
> >
> > Cc: William R Sowerbutts <will@sowerbutts.com>
> > Cc: Finn Thain <fthain@linux-m68k.org>
> > Cc: Geert Uytterhoeven <geert@linux-m68k.org>
> > Tested-by: William R Sowerbutts <will@sowerbutts.com>
> > Signed-off-by: Michael Schmitz <schmitzmic@gmail.com>
> >
> > ---
> >
> > Changes since v2:
> >
> > Geert Uytterhoeven:
> > - only shift swap bitmask if pdev->id > 0
>
> Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>

Oops, I meant
Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
But it never hurts to have more review tags ;-)

Gr{oetje,eeting}s,

                        Geert
Sergey Shtylyov Aug. 23, 2023, 4:35 p.m. UTC | #3 
On 8/23/23 1:13 AM, Michael Schmitz wrote:

> Some users of pata_falcon on Q40 have IDE disks in default
> IDE little endian byte order, whereas legacy disks use
> host-native big-endian byte order as on the Atari Falcon.
> 
> Add module parameter 'data_swab' to allow connecting drives
> with non-native data byte order. Drives selected by the
> data_swap bit mask will have their user data byte-swapped to
> host byte order, i.e. 'pata_falcon.data_swab=2' will byte-swap
> all user data on drive B, leaving data on drive A in native
> byte order. On Q40, drives on a second IDE interface may be
> added to the bit mask as bits 2 and 3.
> 
> Default setting is no byte swapping, i.e. compatibility with
> the native Falcon or Q40 operating system disk format.
> 
> Cc: William R Sowerbutts <will@sowerbutts.com>
> Cc: Finn Thain <fthain@linux-m68k.org>
> Cc: Geert Uytterhoeven <geert@linux-m68k.org>
> Tested-by: William R Sowerbutts <will@sowerbutts.com>
> Signed-off-by: Michael Schmitz <schmitzmic@gmail.com>

Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>

[...]

> diff --git a/drivers/ata/pata_falcon.c b/drivers/ata/pata_falcon.c
> index 3841ea200bcb..7cf15bd9764a 100644
> --- a/drivers/ata/pata_falcon.c
> +++ b/drivers/ata/pata_falcon.c
[...]
> @@ -194,6 +199,9 @@ static int __init pata_falcon_init_one(struct platform_device *pdev)
>  	ata_port_desc(ap, "cmd %px ctl %px data %pa",
>  		      base, ctl_base, &ap->ioaddr.data_addr);
>  
> +	ap->private_data = (void *)(uintptr_t)(pdev->id > 0 ?
> +		pata_falcon_swap_mask >> 2 : pata_falcon_swap_mask);

   How about:

	ap->private_data = (void *)(uintptr_t)(pata_falcon_swap_mask >>
			   (pdev->id > 0 ? 2 : 0));

[...]

MBR, Sergey
Damien Le Moal Aug. 23, 2023, 11:03 p.m. UTC | #4 
On 8/24/23 01:35, Sergey Shtylyov wrote:
> On 8/23/23 1:13 AM, Michael Schmitz wrote:
> 
>> Some users of pata_falcon on Q40 have IDE disks in default
>> IDE little endian byte order, whereas legacy disks use
>> host-native big-endian byte order as on the Atari Falcon.
>>
>> Add module parameter 'data_swab' to allow connecting drives
>> with non-native data byte order. Drives selected by the
>> data_swap bit mask will have their user data byte-swapped to
>> host byte order, i.e. 'pata_falcon.data_swab=2' will byte-swap
>> all user data on drive B, leaving data on drive A in native
>> byte order. On Q40, drives on a second IDE interface may be
>> added to the bit mask as bits 2 and 3.
>>
>> Default setting is no byte swapping, i.e. compatibility with
>> the native Falcon or Q40 operating system disk format.
>>
>> Cc: William R Sowerbutts <will@sowerbutts.com>
>> Cc: Finn Thain <fthain@linux-m68k.org>
>> Cc: Geert Uytterhoeven <geert@linux-m68k.org>
>> Tested-by: William R Sowerbutts <will@sowerbutts.com>
>> Signed-off-by: Michael Schmitz <schmitzmic@gmail.com>
> 
> Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>
> 
> [...]
> 
>> diff --git a/drivers/ata/pata_falcon.c b/drivers/ata/pata_falcon.c
>> index 3841ea200bcb..7cf15bd9764a 100644
>> --- a/drivers/ata/pata_falcon.c
>> +++ b/drivers/ata/pata_falcon.c
> [...]
>> @@ -194,6 +199,9 @@ static int __init pata_falcon_init_one(struct platform_device *pdev)
>>  	ata_port_desc(ap, "cmd %px ctl %px data %pa",
>>  		      base, ctl_base, &ap->ioaddr.data_addr);
>>  
>> +	ap->private_data = (void *)(uintptr_t)(pdev->id > 0 ?
>> +		pata_falcon_swap_mask >> 2 : pata_falcon_swap_mask);
> 
>    How about:
> 
> 	ap->private_data = (void *)(uintptr_t)(pata_falcon_swap_mask >>
> 			   (pdev->id > 0 ? 2 : 0));

This is so hard to decode... Let's please spell this out.
Something like:

	int shift;

	if (pdev->id)
		shift = 2;
	else
		shift = 0;
	ap->private_data = (uintptr_t)(pata_falcon_swap_mask >> shift);

This is initialization, so no need to try to optimize and rather privilege clear
code.

> 
> [...]
> 
> MBR, Sergey
Michael Schmitz Aug. 24, 2023, 1:49 a.m. UTC | #5 
Hi Damien,

On 24/08/23 11:03, Damien Le Moal wrote:
> On 8/24/23 01:35, Sergey Shtylyov wrote:
>> On 8/23/23 1:13 AM, Michael Schmitz wrote:
>>
>>> Some users of pata_falcon on Q40 have IDE disks in default
>>> IDE little endian byte order, whereas legacy disks use
>>> host-native big-endian byte order as on the Atari Falcon.
>>>
>>> Add module parameter 'data_swab' to allow connecting drives
>>> with non-native data byte order. Drives selected by the
>>> data_swap bit mask will have their user data byte-swapped to
>>> host byte order, i.e. 'pata_falcon.data_swab=2' will byte-swap
>>> all user data on drive B, leaving data on drive A in native
>>> byte order. On Q40, drives on a second IDE interface may be
>>> added to the bit mask as bits 2 and 3.
>>>
>>> Default setting is no byte swapping, i.e. compatibility with
>>> the native Falcon or Q40 operating system disk format.
>>>
>>> Cc: William R Sowerbutts <will@sowerbutts.com>
>>> Cc: Finn Thain <fthain@linux-m68k.org>
>>> Cc: Geert Uytterhoeven <geert@linux-m68k.org>
>>> Tested-by: William R Sowerbutts <will@sowerbutts.com>
>>> Signed-off-by: Michael Schmitz <schmitzmic@gmail.com>
>> Reviewed-by: Sergey Shtylyov <s.shtylyov@omp.ru>
>>
>> [...]
>>
>>> diff --git a/drivers/ata/pata_falcon.c b/drivers/ata/pata_falcon.c
>>> index 3841ea200bcb..7cf15bd9764a 100644
>>> --- a/drivers/ata/pata_falcon.c
>>> +++ b/drivers/ata/pata_falcon.c
>> [...]
>>> @@ -194,6 +199,9 @@ static int __init pata_falcon_init_one(struct platform_device *pdev)
>>>   	ata_port_desc(ap, "cmd %px ctl %px data %pa",
>>>   		      base, ctl_base, &ap->ioaddr.data_addr);
>>>   
>>> +	ap->private_data = (void *)(uintptr_t)(pdev->id > 0 ?
>>> +		pata_falcon_swap_mask >> 2 : pata_falcon_swap_mask);
>>     How about:
>>
>> 	ap->private_data = (void *)(uintptr_t)(pata_falcon_swap_mask >>
>> 			   (pdev->id > 0 ? 2 : 0));
> This is so hard to decode... Let's please spell this out.
> Something like:
>
> 	int shift;
>
> 	if (pdev->id)

Atari Falcon has pdev->id==-1, so this must be 'if (pdev->id > 0)' here.

(Testing for pdev->id nonzero did work in earlier versions of my patch 
because patch 3 changed the platform device ID on Atari. That patch had 
the potential to confuse user space so I dropped it from v3 on.)

> 		shift = 2;
> 	else
> 		shift = 0;

No need for the 'else' if we initialize shift above (as is done for irq, 
io_offset and reg_shift).

> 	ap->private_data = (uintptr_t)(pata_falcon_swap_mask >> shift);
>
> This is initialization, so no need to try to optimize and rather privilege clear
> code.

Hmm - or maybe I'll leave that spelled out as you suggest.

Cheers,

     Michael

>
>> [...]
>>
>> MBR, Sergey
Michael Schmitz Aug. 24, 2023, 1:57 a.m. UTC | #6 
Hi Geert,

On 23/08/23 21:10, Geert Uytterhoeven wrote:
> On Wed, Aug 23, 2023 at 11:10 AM Geert Uytterhoeven
> <geert@linux-m68k.org> wrote:
>> On Wed, Aug 23, 2023 at 12:14 AM Michael Schmitz <schmitzmic@gmail.com> wrote:
>>> Some users of pata_falcon on Q40 have IDE disks in default
>>> IDE little endian byte order, whereas legacy disks use
>>> host-native big-endian byte order as on the Atari Falcon.
>>>
>>> Add module parameter 'data_swab' to allow connecting drives
>>> with non-native data byte order. Drives selected by the
>>> data_swap bit mask will have their user data byte-swapped to
>>> host byte order, i.e. 'pata_falcon.data_swab=2' will byte-swap
>>> all user data on drive B, leaving data on drive A in native
>>> byte order. On Q40, drives on a second IDE interface may be
>>> added to the bit mask as bits 2 and 3.
>>>
>>> Default setting is no byte swapping, i.e. compatibility with
>>> the native Falcon or Q40 operating system disk format.
>>>
>>> Cc: William R Sowerbutts <will@sowerbutts.com>
>>> Cc: Finn Thain <fthain@linux-m68k.org>
>>> Cc: Geert Uytterhoeven <geert@linux-m68k.org>
>>> Tested-by: William R Sowerbutts <will@sowerbutts.com>
>>> Signed-off-by: Michael Schmitz <schmitzmic@gmail.com>
>>>
>>> ---
>>>
>>> Changes since v2:
>>>
>>> Geert Uytterhoeven:
>>> - only shift swap bitmask if pdev->id > 0
>> Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
> Oops, I meant
> Reviewed-by: Geert Uytterhoeven <geert@linux-m68k.org>
> But it never hurts to have more review tags ;-)

Thanks - I can pretty much type that one blind ...

Cheers,

     Michael

>
> Gr{oetje,eeting}s,
>
>                          Geert
>
diff mbox series

Patch

diff --git a/drivers/ata/pata_falcon.c b/drivers/ata/pata_falcon.c
index 3841ea200bcb..7cf15bd9764a 100644
--- a/drivers/ata/pata_falcon.c
+++ b/drivers/ata/pata_falcon.c
@@ -33,6 +33,11 @@ 
 #define DRV_NAME "pata_falcon"
 #define DRV_VERSION "0.1.0"
 
+static int pata_falcon_swap_mask;
+
+module_param_named(data_swab, pata_falcon_swap_mask, int, 0444);
+MODULE_PARM_DESC(data_swab, "Data byte swap enable/disable bitmap (0x1==drive1, 0x2==drive2, 0x4==drive3, 0x8==drive4, default==0)");
+
 static const struct scsi_host_template pata_falcon_sht = {
 	ATA_PIO_SHT(DRV_NAME),
 };
@@ -50,7 +55,7 @@  static unsigned int pata_falcon_data_xfer(struct ata_queued_cmd *qc,
 
 	if (dev->class == ATA_DEV_ATA && cmd &&
 	    !blk_rq_is_passthrough(scsi_cmd_to_rq(cmd)))
-		swap = 0;
+		swap = (uintptr_t)ap->private_data & BIT(dev->devno);
 
 	/* Transfer multiple of 2 bytes */
 	if (rw == READ) {
@@ -194,6 +199,9 @@  static int __init pata_falcon_init_one(struct platform_device *pdev)
 	ata_port_desc(ap, "cmd %px ctl %px data %pa",
 		      base, ctl_base, &ap->ioaddr.data_addr);
 
+	ap->private_data = (void *)(uintptr_t)(pdev->id > 0 ?
+		pata_falcon_swap_mask >> 2 : pata_falcon_swap_mask);
+
 	irq_res = platform_get_resource(pdev, IORESOURCE_IRQ, 0);
 	if (irq_res && irq_res->start > 0) {
 		irq = irq_res->start;