Re: [PATCH v1 09/35] drm/modes: Move named modes parsing to a separate function

From: Geert Uytterhoeven
Date: Fri Aug 12 2022 - 09:27:37 EST


Hi Maxime,

On Fri, Jul 29, 2022 at 6:36 PM Maxime Ripard <maxime@xxxxxxxxxx> wrote:
> The current construction of the named mode parsing doesn't allow to extend
> it easily. Let's move it to a separate function so we can add more
> parameters and modes.
>
> Signed-off-by: Maxime Ripard <maxime@xxxxxxxxxx>

Thanks for your patch, which looks similar to my "[PATCH v2 2/5]
drm/modes: Extract drm_mode_parse_cmdline_named_mode()"
(https://lore.kernel.org/dri-devel/1371554419ae63cb54c2a377db0c1016fcf200bb.1657788997.git.geert@xxxxxxxxxxxxxx
;-)

> --- a/drivers/gpu/drm/drm_modes.c
> +++ b/drivers/gpu/drm/drm_modes.c
> @@ -1773,6 +1773,28 @@ static const char * const drm_named_modes_whitelist[] = {
> "PAL",
> };
>
> +static bool drm_mode_parse_cmdline_named_mode(const char *name,
> + unsigned int name_end,
> + struct drm_cmdline_mode *cmdline_mode)
> +{
> + unsigned int i;
> +
> + for (i = 0; i < ARRAY_SIZE(drm_named_modes_whitelist); i++) {
> + int ret;
> +
> + ret = str_has_prefix(name, drm_named_modes_whitelist[i]);
> + if (ret != name_end)
> + continue;
> +
> + strcpy(cmdline_mode->name, drm_named_modes_whitelist[i]);
> + cmdline_mode->specified = true;
> +
> + return true;
> + }
> +
> + return false;

What's the point in returning a value, if it is never checked?
Just make this function return void?

> +}
> +
> /**
> * drm_mode_parse_command_line_for_connector - parse command line modeline for connector
> * @mode_option: optional per connector mode option
> @@ -1848,18 +1870,14 @@ bool drm_mode_parse_command_line_for_connector(const char *mode_option,
> parse_extras = true;
> }
>
> - /* First check for a named mode */
> - for (i = 0; i < ARRAY_SIZE(drm_named_modes_whitelist); i++) {
> - ret = str_has_prefix(name, drm_named_modes_whitelist[i]);
> - if (ret == mode_end) {
> - if (refresh_ptr)
> - return false; /* named + refresh is invalid */
> + /*
> + * Having a mode that starts by a letter (and thus is named) and
> + * an at-sign (used to specify a refresh rate) is disallowed.
> + */
> + if (!isdigit(name[0]) && refresh_ptr)

This condition may have to be relaxed, if we want to support e.g.
"hd720p@50", cfr. my comments on "[PATCH v1 05/35] drm/connector:
Add TV standard property".

> + return false;
>
> - strcpy(mode->name, drm_named_modes_whitelist[i]);
> - mode->specified = true;
> - break;
> - }
> - }
> + drm_mode_parse_cmdline_named_mode(name, mode_end, mode);

This call needs to be conditional on mode_end being non-zero, cfr. my
patch "[PATCH v2 1/5] drm/modes: parse_cmdline: Handle empty mode name
part" (https://lore.kernel.org/dri-devel/302d0737539daa2053134e8f24fdf37e3d939e1e.1657788997.git.geert@xxxxxxxxxxxxxx).

>
> /* No named mode? Check for a normal mode argument, e.g. 1024x768 */
> if (!mode->specified && isdigit(name[0])) {


Gr{oetje,eeting}s,

Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds