Re: [PATCH] spi: Allow using spi_bitbang_setup() with custom txrx_bufs()
From: Magnus Damm
Date: Thu Nov 26 2009 - 02:50:52 EST
On Thu, Nov 26, 2009 at 4:21 PM, Grant Likely <grant.likely@xxxxxxxxxxxx> wrote:
> On Wed, Nov 25, 2009 at 11:47 PM, Magnus Damm <magnus.damm@xxxxxxxxx> wrote:
>> On Thu, Nov 26, 2009 at 7:15 AM, Grant Likely <grant.likely@xxxxxxxxxxxx> wrote:
>>> On Wed, Nov 25, 2009 at 1:26 AM, Magnus Damm <magnus.damm@xxxxxxxxx> wrote:
>>>> /* per-word shift register access, in hardware or bitbanging */
>>>> - cs->txrx_word = bitbang->txrx_word[spi->mode & (SPI_CPOL|SPI_CPHA)];
>>>> - if (!cs->txrx_word)
>>>> - return -EINVAL;
>>>> + if (bitbang->txrx_bufs == spi_bitbang_bufs) {
>>>> + cs->txrx_word = bitbang->txrx_word[spi->mode & mode_mask];
>>>> + if (!cs->txrx_word)
>>>> + return -EINVAL;
>>>> + }
>>>
>>> Hmmm... this smells like an ugly hack to me. It seems to me that if
>>> some bitbang backend drivers don't want this code, then it should be
>>> encoded into a callback so it can be overridden. Thoughts.
>>
>> Yeah, it's far from clean. I want to make use of spi_bitbang_setup()
>> in my MSIOF driver, but I want to avoid dummy txtx_word[] callbacks
>> that will be unused since i'm using a driver specific
>> bitbang->txrx_bufs function.
>>
>> I guess the attached patch is slightly cleaner? I like the idea of
>> letting bitbang drivers use shared code for
>> spi_bitbang_setup()/spi_bitbang_cleanup() with their private
>> setup_transfer() function which in turn calls
>> spi_bitbang_setup_transfer(). My impression is that there's quite a
>> bit of duplicated setup()/cleanup() code.
>
> This is certainly less ugly. But with the points brought up in the
> other thread, I want to have a close look at spi-bitbang before I
> start applying stuff. It seems nasty. Give me a few days.
Sure, I plan on posting a V2 of the MSIOF driver. I plan to keep the
dummy txrx_word() function for now - this to disconnect the cleanup
from the driver integration, hope that sounds like a good plan.
Cheers,
/ magnus
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