| Message ID | 1404742983-27303-1-git-send-email-linux@roeck-us.net |
|---|---|
| State | Superseded |
| Headers | show |
Hi Guenter, On Mon, 7 Jul 2014 07:23:03 -0700, Guenter Roeck wrote: > SMBus block commands are different to I2C block commands since > the returned data is not normally accessible with byte or word > commands on other command offsets. Add linked list of 'block' > commands to support those commands. > > Access mechanism is quite simple: Block commands must be written > before they can be read. The first write selects the block length. > Subsequent writes can be partial. Block read commands always return > the number of bytes selected with the first write. > > Signed-off-by: Guenter Roeck <linux@roeck-us.net> > --- > v2: Make new functionality only available on request via functionality > module parameter > Add more details about SMBus block mode support to documentation > Use correct sizeof() variable in devm_kzalloc > Use stub_find_block() only in SMBus block command itself. > Store first word of block data in chip->words[]. > When writing block data and the written data is longer than > the first write, bail out with debug message indicating the reason > for the error. Looks good, thanks for the quick update. Reviewed-by: Jean Delvare <jdelvare@suse.de> Just one thing I have been thinking about while reviewing the updated code... You decided to make the first SMBus block write select the maximum block length, and you always use that for SMBus block reads. However you accept partial writes. The fact that the order in which writes are performed has an effect on which writes are accepted is somewhat unexpected. Wouldn't it make more sense to accept all SMBus block writes, regardless of the size (as long as it is within the limits of the SMBus standard, of course)? Then the only thing left to decide is whether SMBus block reads use the maximum size or the size of the most recent SMBus block write. I suspect this would mimic the behavior of real chips better. What do you think?
Hi Jean, On 07/08/2014 12:54 PM, Jean Delvare wrote: > Hi Guenter, > > On Mon, 7 Jul 2014 07:23:03 -0700, Guenter Roeck wrote: >> SMBus block commands are different to I2C block commands since >> the returned data is not normally accessible with byte or word >> commands on other command offsets. Add linked list of 'block' >> commands to support those commands. >> >> Access mechanism is quite simple: Block commands must be written >> before they can be read. The first write selects the block length. >> Subsequent writes can be partial. Block read commands always return >> the number of bytes selected with the first write. >> >> Signed-off-by: Guenter Roeck <linux@roeck-us.net> >> --- >> v2: Make new functionality only available on request via functionality >> module parameter >> Add more details about SMBus block mode support to documentation >> Use correct sizeof() variable in devm_kzalloc >> Use stub_find_block() only in SMBus block command itself. >> Store first word of block data in chip->words[]. >> When writing block data and the written data is longer than >> the first write, bail out with debug message indicating the reason >> for the error. > > Looks good, thanks for the quick update. > > Reviewed-by: Jean Delvare <jdelvare@suse.de> > > Just one thing I have been thinking about while reviewing the updated > code... You decided to make the first SMBus block write select the > maximum block length, and you always use that for SMBus block reads. > However you accept partial writes. The fact that the order in which > writes are performed has an effect on which writes are accepted is > somewhat unexpected. > > Wouldn't it make more sense to accept all SMBus block writes, > regardless of the size (as long as it is within the limits of the SMBus > standard, of course)? Then the only thing left to decide is whether > SMBus block reads use the maximum size or the size of the most recent > SMBus block write. > > I suspect this would mimic the behavior of real chips better. What do > you think? > Not really sure what the expected behavior is. My original code accepted all writes and returned the most recent write, including the most recent write length. I thought this was untypical, and that it would be more typical for the chip to return a fixed length. But ultimately I don't really know, and I am fine either way. Guenter -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Mon, Jul 07, 2014 at 07:23:03AM -0700, Guenter Roeck wrote: > SMBus block commands are different to I2C block commands since > the returned data is not normally accessible with byte or word > commands on other command offsets. Add linked list of 'block' > commands to support those commands. > > Access mechanism is quite simple: Block commands must be written > before they can be read. The first write selects the block length. > Subsequent writes can be partial. Block read commands always return > the number of bytes selected with the first write. > > Signed-off-by: Guenter Roeck <linux@roeck-us.net> > --- > v2: Make new functionality only available on request via functionality > module parameter > Add more details about SMBus block mode support to documentation > Use correct sizeof() variable in devm_kzalloc > Use stub_find_block() only in SMBus block command itself. > Store first word of block data in chip->words[]. > When writing block data and the written data is longer than > the first write, bail out with debug message indicating the reason > for the error. Thanks for doing this and thanks to Jean for the thorough review. The thing I miss is the documentation that SMBUS_BLOCK must explicitly be activated and the description how to do it. A comment in the driver, above STUB_FUNC_* defines might not hurt as well. Also, I'd prefer to squash Jean's "increasing block length" patch into this one if both of you are fine with that? Regards, Wolfram
On Thu, 17 Jul 2014 15:21:35 +0200, Wolfram Sang wrote: > On Mon, Jul 07, 2014 at 07:23:03AM -0700, Guenter Roeck wrote: > > SMBus block commands are different to I2C block commands since > > the returned data is not normally accessible with byte or word > > commands on other command offsets. Add linked list of 'block' > > commands to support those commands. > > > > Access mechanism is quite simple: Block commands must be written > > before they can be read. The first write selects the block length. > > Subsequent writes can be partial. Block read commands always return > > the number of bytes selected with the first write. > > > > Signed-off-by: Guenter Roeck <linux@roeck-us.net> > > --- > > v2: Make new functionality only available on request via functionality > > module parameter > > Add more details about SMBus block mode support to documentation > > Use correct sizeof() variable in devm_kzalloc > > Use stub_find_block() only in SMBus block command itself. > > Store first word of block data in chip->words[]. > > When writing block data and the written data is longer than > > the first write, bail out with debug message indicating the reason > > for the error. > > Thanks for doing this and thanks to Jean for the thorough review. You're welcome. > The thing I miss is the documentation that SMBUS_BLOCK must explicitly > be activated and the description how to do it. A comment in the driver, > above STUB_FUNC_* defines might not hurt as well. Good point. > Also, I'd prefer to squash Jean's "increasing block length" patch into > this one if both of you are fine with that? Yes, I would be perfectly fine with that. Guenter, can you please send an updated patch?
diff --git a/Documentation/i2c/i2c-stub b/Documentation/i2c/i2c-stub index fa4b669..531510b 100644 --- a/Documentation/i2c/i2c-stub +++ b/Documentation/i2c/i2c-stub @@ -2,9 +2,9 @@ MODULE: i2c-stub DESCRIPTION: -This module is a very simple fake I2C/SMBus driver. It implements five +This module is a very simple fake I2C/SMBus driver. It implements six types of SMBus commands: write quick, (r/w) byte, (r/w) byte data, (r/w) -word data, and (r/w) I2C block data. +word data, (r/w) I2C block data, and (r/w) SMBus block data. You need to provide chip addresses as a module parameter when loading this driver, which will then only react to SMBus commands to these addresses. @@ -19,6 +19,11 @@ A pointer register with auto-increment is implemented for all byte operations. This allows for continuous byte reads like those supported by EEPROMs, among others. +SMBus block commands must be written to configure an SMBus command for +SMBus block operations. The first SMBus block write selects the block length. +Subsequent writes can be partial. Block read commands always return +the number of bytes selected with the first write. + The typical use-case is like this: 1. load this module 2. use i2cset (from the i2c-tools project) to pre-load some data diff --git a/drivers/i2c/i2c-stub.c b/drivers/i2c/i2c-stub.c index 77e4849..4fbe565 100644 --- a/drivers/i2c/i2c-stub.c +++ b/drivers/i2c/i2c-stub.c @@ -27,29 +27,64 @@ #include <linux/slab.h> #include <linux/errno.h> #include <linux/i2c.h> +#include <linux/list.h> #define MAX_CHIPS 10 -#define STUB_FUNC (I2C_FUNC_SMBUS_QUICK | I2C_FUNC_SMBUS_BYTE | \ - I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA | \ - I2C_FUNC_SMBUS_I2C_BLOCK) +#define STUB_FUNC_DEFAULT \ + (I2C_FUNC_SMBUS_QUICK | I2C_FUNC_SMBUS_BYTE | \ + I2C_FUNC_SMBUS_BYTE_DATA | I2C_FUNC_SMBUS_WORD_DATA | \ + I2C_FUNC_SMBUS_I2C_BLOCK) + +#define STUB_FUNC_ALL \ + (STUB_FUNC_DEFAULT | I2C_FUNC_SMBUS_BLOCK_DATA) static unsigned short chip_addr[MAX_CHIPS]; module_param_array(chip_addr, ushort, NULL, S_IRUGO); MODULE_PARM_DESC(chip_addr, "Chip addresses (up to 10, between 0x03 and 0x77)"); -static unsigned long functionality = STUB_FUNC; +static unsigned long functionality = STUB_FUNC_DEFAULT; module_param(functionality, ulong, S_IRUGO | S_IWUSR); MODULE_PARM_DESC(functionality, "Override functionality bitfield"); +struct smbus_block_data { + struct list_head node; + u8 command; + u8 len; + u8 block[I2C_SMBUS_BLOCK_MAX]; +}; + struct stub_chip { u8 pointer; u16 words[256]; /* Byte operations use the LSB as per SMBus specification */ + struct list_head smbus_blocks; }; static struct stub_chip *stub_chips; +static struct smbus_block_data *stub_find_block(struct device *dev, + struct stub_chip *chip, + u8 command, bool create) +{ + struct smbus_block_data *b, *rb = NULL; + + list_for_each_entry(b, &chip->smbus_blocks, node) { + if (b->command == command) { + rb = b; + break; + } + } + if (rb == NULL && create) { + rb = devm_kzalloc(dev, sizeof(*rb), GFP_KERNEL); + if (rb == NULL) + return rb; + rb->command = command; + list_add(&rb->node, &chip->smbus_blocks); + } + return rb; +} + /* Return negative errno on error. */ static s32 stub_xfer(struct i2c_adapter *adap, u16 addr, unsigned short flags, char read_write, u8 command, int size, union i2c_smbus_data *data) @@ -57,6 +92,7 @@ static s32 stub_xfer(struct i2c_adapter *adap, u16 addr, unsigned short flags, s32 ret; int i, len; struct stub_chip *chip = NULL; + struct smbus_block_data *b; /* Search for the right chip */ for (i = 0; i < MAX_CHIPS && chip_addr[i]; i++) { @@ -148,6 +184,57 @@ static s32 stub_xfer(struct i2c_adapter *adap, u16 addr, unsigned short flags, ret = 0; break; + case I2C_SMBUS_BLOCK_DATA: + b = stub_find_block(&adap->dev, chip, command, false); + if (read_write == I2C_SMBUS_WRITE) { + len = data->block[0]; + if (len == 0 || len > I2C_SMBUS_BLOCK_MAX) { + ret = -EINVAL; + break; + } + if (b && len > b->len) { + dev_dbg(&adap->dev, + "Attempt to write more data (%d) than with initial SMBus block write (%d)\n", + len, b->len); + ret = -EINVAL; + break; + } + if (b == NULL) { + b = stub_find_block(&adap->dev, chip, command, + true); + if (b == NULL) { + ret = -ENOMEM; + break; + } + /* First write sets block length */ + b->len = len; + } + for (i = 0; i < len; i++) + b->block[i] = data->block[i + 1]; + /* update for byte and word commands */ + chip->words[command] = (b->block[0] << 8) | b->len; + dev_dbg(&adap->dev, + "smbus block data - addr 0x%02x, wrote %d bytes at 0x%02x.\n", + addr, len, command); + } else { + if (b == NULL) { + dev_dbg(&adap->dev, + "SMBus block read command without prior block write not supported\n"); + ret = -EOPNOTSUPP; + break; + } + len = b->len; + data->block[0] = len; + for (i = 0; i < len; i++) + data->block[i + 1] = b->block[i]; + dev_dbg(&adap->dev, + "smbus block data - addr 0x%02x, read %d bytes at 0x%02x.\n", + addr, len, command); + } + + ret = 0; + break; + default: dev_dbg(&adap->dev, "Unsupported I2C/SMBus command\n"); ret = -EOPNOTSUPP; @@ -159,7 +246,7 @@ static s32 stub_xfer(struct i2c_adapter *adap, u16 addr, unsigned short flags, static u32 stub_func(struct i2c_adapter *adapter) { - return STUB_FUNC & functionality; + return STUB_FUNC_ALL & functionality; } static const struct i2c_algorithm smbus_algorithm = { @@ -199,6 +286,8 @@ static int __init i2c_stub_init(void) pr_err("i2c-stub: Out of memory\n"); return -ENOMEM; } + for (i--; i >= 0; i--) + INIT_LIST_HEAD(&stub_chips[i].smbus_blocks); ret = i2c_add_adapter(&stub_adapter); if (ret)
SMBus block commands are different to I2C block commands since the returned data is not normally accessible with byte or word commands on other command offsets. Add linked list of 'block' commands to support those commands. Access mechanism is quite simple: Block commands must be written before they can be read. The first write selects the block length. Subsequent writes can be partial. Block read commands always return the number of bytes selected with the first write. Signed-off-by: Guenter Roeck <linux@roeck-us.net> --- v2: Make new functionality only available on request via functionality module parameter Add more details about SMBus block mode support to documentation Use correct sizeof() variable in devm_kzalloc Use stub_find_block() only in SMBus block command itself. Store first word of block data in chip->words[]. When writing block data and the written data is longer than the first write, bail out with debug message indicating the reason for the error. Documentation/i2c/i2c-stub | 9 ++++- drivers/i2c/i2c-stub.c | 99 +++++++++++++++++++++++++++++++++++++++++++--- 2 files changed, 101 insertions(+), 7 deletions(-)