Le 28/02/2022 à 16:29, Mark Brown a écrit :
> On Mon, Feb 28, 2022 at 04:15:46PM +0100, Christophe Leroy wrote:
>
>> + if (!status && spi->trailing_bits) {
>> + struct spi_transfer t = {
>> + .len = 1,
>> + .tx_buf = empty_zero_page,
>> + };
>> +
>> + if (spi->trailing_bits < 4)
>> + t.bits_per_word = 4;
>> + else if (spi->trailing_bits > 8)
>> + t.bits_per_word = 16;
>> + else
>> + t.bits_per_word = spi->trailing_bits;
>> +
>> + status = fsl_spi_setup_transfer(spi, &t);
>> + if (!status)
>> + status = fsl_spi_bufs(spi, &t, 0);
>> + }
>> + m->status = status;
>
> The binding looks good now but this is still driver specific code when
> it looks like it could easily be implemented in the core - like I said
> on the previous version you'd need to update drivers to advertise less
> than 8 bits but there's basically nothing driver specific I can see here
> so any driver using transfer_one() would get support that way.
Argh ! Sorry your comment to the previous version ended up in Junk
mails. I see it now.
We discussed that back in 2016 in
https://lore.kernel.org/linux-spi/20160824112701.GE22076@xxxxxxxxxxxxx/
and my understanding at that time was that it was not something that
could be done at core level.
But maybe things have changed since then ?
By the way, fsl-spi driver doesn't implement transfer_one() but
transfer_one_message() so it takes care of the chipselect changes and
therefore the final dummy transfer with CS off is to be done there as
far as I understand.
Would it mean changing fsl-spi driver to implement transfer_one() first ?
Thanks
Christophe
