linux-kernel - Re: [PATCH 2/5] drm/modes: Extract drm_mode_parse_cmdline_named

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Date:   Fri, 8 Jul 2022 21:45:58 +0200
From:   Hans de Goede <hdegoede@...hat.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>
Cc:     dri-devel@...ts.freedesktop.org, linux-fbdev@...r.kernel.org,
        linux-m68k@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/5] drm/modes: Extract
 drm_mode_parse_cmdline_named_mode()

Hi,

On 7/8/22 20:21, Geert Uytterhoeven wrote:
> Extract the code to check for a named mode parameter into its own
> function, to streamline the main parsing flow.
> 
> Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> ---
>  drivers/gpu/drm/drm_modes.c | 41 +++++++++++++++++++++++++++----------
>  1 file changed, 30 insertions(+), 11 deletions(-)
> 
> diff --git a/drivers/gpu/drm/drm_modes.c b/drivers/gpu/drm/drm_modes.c
> index 30a7be97707bfb16..434383469e9d984d 100644
> --- a/drivers/gpu/drm/drm_modes.c
> +++ b/drivers/gpu/drm/drm_modes.c
> @@ -1749,6 +1749,30 @@ static const char * const drm_named_modes_whitelist[] = {
>  	"PAL",
>  };
>  
> +static int drm_mode_parse_cmdline_named_mode(const char *name,
> +					     unsigned int length,
> +					     bool refresh,
> +					     struct drm_cmdline_mode *mode)
> +{
> +	unsigned int i;
> +	int ret;
> +
> +	for (i = 0; i < ARRAY_SIZE(drm_named_modes_whitelist); i++) {
> +		ret = str_has_prefix(name, drm_named_modes_whitelist[i]);
> +		if (!ret)

As discussed in my review of 1/5 this needs to become:

		if (ret != length)
> +			continue;

Which renders my other comment on this patch (length not being used) mute.

Regards,

Hans

> +
> +		if (refresh)
> +			return -EINVAL; /* named + refresh is invalid */
> +
> +		strcpy(mode->name, drm_named_modes_whitelist[i]);
> +		mode->specified = true;
> +		return 0;
> +	}
> +
> +	return 0;
> +}
> +
>  /**
>   * drm_mode_parse_command_line_for_connector - parse command line modeline for connector
>   * @mode_option: optional per connector mode option
> @@ -1785,7 +1809,7 @@ bool drm_mode_parse_command_line_for_connector(const char *mode_option,
>  	const char *bpp_ptr = NULL, *refresh_ptr = NULL, *extra_ptr = NULL;
>  	const char *options_ptr = NULL;
>  	char *bpp_end_ptr = NULL, *refresh_end_ptr = NULL;
> -	int i, len, ret;
> +	int len, ret;
>  
>  	memset(mode, 0, sizeof(*mode));
>  	mode->panel_orientation = DRM_MODE_PANEL_ORIENTATION_UNKNOWN;
> @@ -1823,16 +1847,11 @@ bool drm_mode_parse_command_line_for_connector(const char *mode_option,
>  	}
>  
>  	/* First check for a named mode */
> -	for (i = 0; mode_end && i < ARRAY_SIZE(drm_named_modes_whitelist); i++) {
> -		ret = str_has_prefix(name, drm_named_modes_whitelist[i]);
> -		if (ret) {
> -			if (refresh_ptr)
> -				return false; /* named + refresh is invalid */
> -
> -			strcpy(mode->name, drm_named_modes_whitelist[i]);
> -			mode->specified = true;
> -			break;
> -		}
> +	if (mode_end) {
> +		ret = drm_mode_parse_cmdline_named_mode(name, mode_end,
> +							refresh_ptr, mode);
> +		if (ret)
> +			return false;
>  	}
>  
>  	/* No named mode? Check for a normal mode argument, e.g. 1024x768 */