[U-Boot] [PATCH v2] spi: soft_spi: Support NULL din/dout buffers

[Jagan Teki]

On Fri, Apr 25, 2014 at 12:09 AM, Andrew Ruder
<andrew.ruder at elecsyscorp.com> wrote:
> This mirrors the conventions used in other SPI drivers (kirkwood,
> davinci, atmel, et al) where the din/dout buffer can be NULL when the
> received/transmitted data isn't important.  This reduces the need for
> allocating additional buffers when write-only/read-only functionality is
> needed.
>
> In the din == NULL case, the received data is simply not stored.  In the
> dout == NULL case, zeroes are transmitted.
>
> Signed-off-by: Andrew Ruder <andrew.ruder at elecsyscorp.com>
> Cc: Jean-Christophe PLAGNIOL-VILLARD <plagnioj at jcrosoft.com>
> Cc: Jagan Teki <jagannadh.teki at gmail.com>
> ---
> Cleaned up errors/warnings from checkpatch.pl.  I'm surprised they were flagged
> by the script since the actual ERRORs were all on lines I didn't change but were
> only included in the context.
>
> scripts/checkpatch.pl 0001-spi-soft_spi-Support-NULL-din-dout-buffers.patch
> total: 0 errors, 0 warnings, 0 checks, 31 lines checked
>
>  drivers/spi/soft_spi.c | 18 ++++++++++++------
>  1 file changed, 12 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/spi/soft_spi.c b/drivers/spi/soft_spi.c
> index 5d22351..c969be3 100644
> --- a/drivers/spi/soft_spi.c
> +++ b/drivers/spi/soft_spi.c
> @@ -136,10 +136,14 @@ int  spi_xfer(struct spi_slave *slave, unsigned int bitlen,
>                 /*
>                  * Check if it is time to work on a new byte.
>                  */
> -               if((j % 8) == 0) {
> -                       tmpdout = *txd++;
> +               if ((j % 8) == 0) {
> +                       if (txd)
> +                               tmpdout = *txd++;
> +                       else
> +                               tmpdout = 0;
>                         if(j != 0) {
> -                               *rxd++ = tmpdin;
> +                               if (rxd)
> +                                       *rxd++ = tmpdin;
>                         }
>                         tmpdin  = 0;
>                 }
> @@ -164,9 +168,11 @@ int  spi_xfer(struct spi_slave *slave, unsigned int bitlen,
>          * bits over to left-justify them.  Then store the last byte
>          * read in.
>          */
> -       if((bitlen % 8) != 0)
> -               tmpdin <<= 8 - (bitlen % 8);
> -       *rxd++ = tmpdin;
> +       if (rxd) {
> +               if ((bitlen % 8) != 0)
> +                       tmpdin <<= 8 - (bitlen % 8);
> +               *rxd++ = tmpdin;
> +       }
>
>         if (flags & SPI_XFER_END)
>                 spi_cs_deactivate(slave);
> --
> 1.9.0.rc3.12.gbc97e2d
>

Applied to u-boot-spi/master

thanks!
-- 
Jagan.