[PATCH v3] drm/dbi: Print errors for mipi_dbi_command()

[Noralf Trønnes]

Den 02.07.2021 15.56, skrev Linus Walleij:
> The macro mipi_dbi_command() does not report errors unless you wrap it
> in another macro to do the error reporting.
> 
> Report a rate-limited error so we know what is going on.
> 
> Drop the only user in DRM using mipi_dbi_command() and actually checking
> the error explicitly, let it use mipi_dbi_command_buf() directly
> instead.

You forgot to remove this section.

With that fixed:

Reviewed-by: Noralf Trønnes <noralf at tronnes.org>

> 
> After this any code wishing to send command arrays can rely on
> mipi_dbi_command() providing an appropriate error message if something
> goes wrong.
> 
> Suggested-by: Noralf Trønnes <noralf at tronnes.org>
> Suggested-by: Douglas Anderson <dianders at chromium.org>
> Signed-off-by: Linus Walleij <linus.walleij at linaro.org>
> ---
> ChangeLog v2->v3:
> - Make the macro actually return the error value if need be, by
>   putting a single ret; at the end of the macro. (Neat trick from
>   StackOverflow!)
> - Switch the site where I switched mipi_dbi_command() to
>   mipi_dbi_command_buf() back to what it was.
> - Print the failed command in the error message.
> - Put the dbi in (parens) since drivers/gpu/drm/tiny/st7586.c was
>   passing &dbidev->dbi as parameter to mipi_dbi_command()
>   and this would expand to
>   struct device *dev = &&dbidev->dbi->spi->dev
>   which can't be parsed but
>   struct device *dev = &(&dbidev->dbi)->spi-dev;
>   should work. I hope.
> ChangeLog v1->v2:
> - Fish out the struct device * from the DBI SPI client and use
>   that to print the errors associated with the SPI device.
> ---
>  include/drm/drm_mipi_dbi.h | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/include/drm/drm_mipi_dbi.h b/include/drm/drm_mipi_dbi.h
> index f543d6e3e822..05e194958265 100644
> --- a/include/drm/drm_mipi_dbi.h
> +++ b/include/drm/drm_mipi_dbi.h
> @@ -183,7 +183,12 @@ int mipi_dbi_buf_copy(void *dst, struct drm_framebuffer *fb,
>  #define mipi_dbi_command(dbi, cmd, seq...) \
>  ({ \
>  	const u8 d[] = { seq }; \
> -	mipi_dbi_command_stackbuf(dbi, cmd, d, ARRAY_SIZE(d)); \
> +	struct device *dev = &(dbi)->spi->dev;	\
> +	int ret; \
> +	ret = mipi_dbi_command_stackbuf(dbi, cmd, d, ARRAY_SIZE(d)); \
> +	if (ret) \
> +		dev_err_ratelimited(dev, "error %d when sending command %#02x\n", ret, cmd); \
> +	ret; \
>  })
>  
>  #ifdef CONFIG_DEBUG_FS
>