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

[Jagan Teki]

Hi Andrew Ruder,

On Wed, Oct 23, 2013 at 5:41 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>
> ---
>  drivers/spi/soft_spi.c | 18 +++++++++++++-----
>  1 file changed, 13 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/spi/soft_spi.c b/drivers/spi/soft_spi.c
> index 5d22351..5fdd091 100644
> --- a/drivers/spi/soft_spi.c
> +++ b/drivers/spi/soft_spi.c
> @@ -137,9 +137,15 @@ 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 (txd) {
> +                               tmpdout = *txd++;
> +                       } else {
> +                               tmpdout = 0;
> +                       }
>                         if(j != 0) {
> -                               *rxd++ = tmpdin;
> +                               if (rxd) {
> +                                       *rxd++ = tmpdin;
> +                               }
>                         }
>                         tmpdin  = 0;
>                 }
> @@ -164,9 +170,11 @@ 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);
> --

I'm not sure does this NULL buf config stuff will works all boards as
you listed.
I guess ie the reason the earlier code doesn't have this.

Does this tested on your board? any possibility to test others too.

Jean-Christophe, any comments here!

-- 
Thanks,
Jagan.