On 04. 06. 19 23:55, Robert Hancock wrote:
> This driver does not support reading more than 255 bytes at once because
> the register for storing the number of bytes to read is only 8 bits. Add
> a max_read_len quirk to enforce this.
>
> This was found when using this driver with the SFP driver, which was
> previously reading all 256 bytes in the SFP EEPROM in one transaction.
> This caused a bunch of hard-to-debug errors in the xiic driver since the
> driver/logic was treating the number of bytes to read as zero.
> Rejecting transactions that aren't supported at least allows the problem
> to be diagnosed more easily.
>
> Signed-off-by: Robert Hancock <hancock@xxxxxxxxxxxxx>
> ---
>
> Changes since v1: Added more rationale in description.
>
> drivers/i2c/busses/i2c-xiic.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/drivers/i2c/busses/i2c-xiic.c b/drivers/i2c/busses/i2c-xiic.c
> index 0fea7c5..37b3b93 100644
> --- a/drivers/i2c/busses/i2c-xiic.c
> +++ b/drivers/i2c/busses/i2c-xiic.c
> @@ -709,11 +709,16 @@ static u32 xiic_func(struct i2c_adapter *adap)
> .functionality = xiic_func,
> };
>
> +static const struct i2c_adapter_quirks xiic_quirks = {
> + .max_read_len = 255,
> +};
> +
> static const struct i2c_adapter xiic_adapter = {
> .owner = THIS_MODULE,
> .name = DRIVER_NAME,
> .class = I2C_CLASS_DEPRECATED,
> .algo = &xiic_algorithm,
> + .quirks = &xiic_quirks,
> };
>
Reviewed-by: Michal Simek <michal.simek@xxxxxxxxxx>
Nit: The same limitation is there for write. Maybe worth to also set it
up. Anyway this can be done separately.
Thanks,
Michal
