linux-kernel - Re: [PATCH RFC 1/7] drm/mipi-dsi: wrap more functions for streamline handling

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Date: Fri, 10 May 2024 14:45:45 -0700
From: Doug Anderson <dianders@...omium.org>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, 
	Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>, 
	Neil Armstrong <neil.armstrong@...aro.org>, Jessica Zhang <quic_jesszhan@...cinc.com>, 
	Sam Ravnborg <sam@...nborg.org>, Sumit Semwal <sumit.semwal@...aro.org>, 
	Caleb Connolly <caleb.connolly@...aro.org>, Marijn Suijten <marijn.suijten@...ainline.org>, 
	Vinod Koul <vkoul@...nel.org>, dri-devel@...ts.freedesktop.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC 1/7] drm/mipi-dsi: wrap more functions for streamline handling

Hi,

On Thu, May 9, 2024 at 3:37 PM Dmitry Baryshkov
<dmitry.baryshkov@...aro.org> wrote:
>
> +/**
> + * mipi_dsi_compression_mode_ext() - enable/disable DSC on the peripheral
> + * @ctx: Context for multiple DSI transactions
> + * @enable: Whether to enable or disable the DSC
> + * @algo: Selected compression algorithm
> + * @pps_selector: Select PPS from the table of pre-stored or uploaded PPS entries
> + *
> + * Like mipi_dsi_compression_mode_ext_multi() but deals with errors in a way that
> + * makes it convenient to make several calls in a row.

Your comment is backward. The name of the function is
mipi_dsi_compression_mode_ext_multi() not
mipi_dsi_compression_mode_ext(). ...and it's like
mipi_dsi_compression_mode_ext() not like
mipi_dsi_compression_mode_ext_multi().


> @@ -338,6 +345,18 @@ int mipi_dsi_dcs_set_display_brightness_large(struct mipi_dsi_device *dsi,
>  int mipi_dsi_dcs_get_display_brightness_large(struct mipi_dsi_device *dsi,
>                                              u16 *brightness);
>
> +void mipi_dsi_dcs_nop_multi(struct mipi_dsi_multi_context *ctx);
> +void mipi_dsi_dcs_enter_sleep_mode_multi(struct mipi_dsi_multi_context *ctx);
> +void mipi_dsi_dcs_exit_sleep_mode_multi(struct mipi_dsi_multi_context *ctx);
> +void mipi_dsi_dcs_set_display_off_multi(struct mipi_dsi_multi_context *ctx);
> +void mipi_dsi_dcs_set_display_on_multi(struct mipi_dsi_multi_context *ctx);
> +void mipi_dsi_dcs_set_tear_on_multi(struct mipi_dsi_multi_context *ctx,
> +                                   enum mipi_dsi_dcs_tear_mode mode);
> +
> +#define mipi_dsi_msleep(ctx, delay)    \
> +       if (!ctx.accum_err)             \
> +               msleep(delay)           \

Please enclose the above in a "do { ... } while (0)" as typical for
macros. Otherwise you could possibly get some very surprising
behavior:

if (needs_big_delay)
  mipi_dsi_msleep(ctx, 50)
else
  mipi_dsi_msleep(ctx, 10)

..with your macro as it is I think the "else" will match up against
the "if !(ctx.accum_err)" inside the macro and not against the "if
(needs_big_delay)"

Also: nit that the mipi_dsi_msleep() should probably be defined above
the "mipi_dsi_dcs" section.


-Doug