linux-kernel - Re: [PATCH v5 12/22] drm/connector: Add a function to lookup a TV mode by its name

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Message-ID: <7dcf479c-8ac7-ed47-8587-30268684373c@tronnes.org>
Date:   Mon, 17 Oct 2022 12:44:45 +0200
From:   Noralf Trønnes <noralf@...nnes.org>
To:     Maxime Ripard <maxime@...no.tech>,
        Karol Herbst <kherbst@...hat.com>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        David Airlie <airlied@...ux.ie>,
        Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
        Lyude Paul <lyude@...hat.com>,
        Maxime Ripard <mripard@...nel.org>,
        Emma Anholt <emma@...olt.net>, Chen-Yu Tsai <wens@...e.org>,
        Samuel Holland <samuel@...lland.org>,
        Ben Skeggs <bskeggs@...hat.com>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        Rodrigo Vivi <rodrigo.vivi@...el.com>,
        Jernej Skrabec <jernej.skrabec@...il.com>
Cc:     Dom Cobley <dom@...pberrypi.com>, linux-sunxi@...ts.linux.dev,
        Dave Stevenson <dave.stevenson@...pberrypi.com>,
        intel-gfx@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        nouveau@...ts.freedesktop.org,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        linux-arm-kernel@...ts.infradead.org,
        Mateusz Kwiatkowski <kfyatek+publicgit@...il.com>,
        dri-devel@...ts.freedesktop.org,
        Hans de Goede <hdegoede@...hat.com>,
        Phil Elwell <phil@...pberrypi.com>,
        Noralf Trønnes <noralf@...nnes.org>
Subject: Re: [PATCH v5 12/22] drm/connector: Add a function to lookup a TV
 mode by its name



Den 13.10.2022 15.18, skrev Maxime Ripard:
> As part of the command line parsing rework coming in the next patches,
> we'll need to lookup drm_connector_tv_mode values by their name, already
> defined in drm_tv_mode_enum_list.
> 
> In order to avoid any code duplication, let's do a function that will
> perform a lookup of a TV mode name and return its value.
> 
> Signed-off-by: Maxime Ripard <maxime@...no.tech>
> ---
>  drivers/gpu/drm/drm_connector.c | 24 ++++++++++++++++++++++++
>  include/drm/drm_connector.h     |  2 ++
>  2 files changed, 26 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> index 820f4c730b38..30611c616435 100644
> --- a/drivers/gpu/drm/drm_connector.c
> +++ b/drivers/gpu/drm/drm_connector.c
> @@ -991,6 +991,30 @@ static const struct drm_prop_enum_list drm_tv_mode_enum_list[] = {
>  };
>  DRM_ENUM_NAME_FN(drm_get_tv_mode_name, drm_tv_mode_enum_list)
>  
> +/**
> + * drm_get_tv_mode_from_name - Translates a TV mode name into its enum value
> + * @name: TV Mode name we want to convert
> + * @len: Length of @name
> + *
> + * Translates @name into an enum drm_connector_tv_mode.
> + *
> + * Returns: the enum value on success, a negative errno otherwise.
> + */
> +int drm_get_tv_mode_from_name(const char *name, size_t len)

Do we really need to pass in length here?
item->name has to always be NUL terminated otherwise things would break
elsewhere, so it shouldn't be necessary AFAICS.

Noralf.

> +{
> +	unsigned int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(drm_tv_mode_enum_list); i++) {
> +		const struct drm_prop_enum_list *item = &drm_tv_mode_enum_list[i];
> +
> +		if (strlen(item->name) == len && !strncmp(item->name, name, len))
> +			return item->type;
> +	}
> +
> +	return -EINVAL;
> +}
> +EXPORT_SYMBOL(drm_get_tv_mode_from_name);
> +
>  static const struct drm_prop_enum_list drm_tv_select_enum_list[] = {
>  	{ DRM_MODE_SUBCONNECTOR_Automatic, "Automatic" }, /* DVI-I and TV-out */
>  	{ DRM_MODE_SUBCONNECTOR_Composite, "Composite" }, /* TV-out */
> diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> index a501db7d2222..a33f24a76738 100644
> --- a/include/drm/drm_connector.h
> +++ b/include/drm/drm_connector.h
> @@ -1864,6 +1864,8 @@ const char *drm_get_dp_subconnector_name(int val);
>  const char *drm_get_content_protection_name(int val);
>  const char *drm_get_hdcp_content_type_name(int val);
>  
> +int drm_get_tv_mode_from_name(const char *name, size_t len);
> +
>  int drm_mode_create_dvi_i_properties(struct drm_device *dev);
>  void drm_connector_attach_dp_subconnector_property(struct drm_connector *connector);
>  
>