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Message-ID: <842076aa-8d7c-96d6-ba46-d0e66dacd2df@tronnes.org>
Date: Sun, 6 Nov 2022 17:33:48 +0100
From: Noralf Trønnes <noralf@...nnes.org>
To: maxime@...no.tech, Karol Herbst <kherbst@...hat.com>,
Emma Anholt <emma@...olt.net>, Ben Skeggs <bskeggs@...hat.com>,
Chen-Yu Tsai <wens@...e.org>,
Rodrigo Vivi <rodrigo.vivi@...el.com>,
Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
Jani Nikula <jani.nikula@...ux.intel.com>,
Daniel Vetter <daniel@...ll.ch>,
Thomas Zimmermann <tzimmermann@...e.de>,
Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
Samuel Holland <samuel@...lland.org>,
Jernej Skrabec <jernej.skrabec@...il.com>,
David Airlie <airlied@...ux.ie>,
Maxime Ripard <mripard@...nel.org>,
Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
Lyude Paul <lyude@...hat.com>
Cc: linux-sunxi@...ts.linux.dev, intel-gfx@...ts.freedesktop.org,
Phil Elwell <phil@...pberrypi.com>,
linux-arm-kernel@...ts.infradead.org,
nouveau@...ts.freedesktop.org, Hans de Goede <hdegoede@...hat.com>,
Dom Cobley <dom@...pberrypi.com>,
Mateusz Kwiatkowski <kfyatek+publicgit@...il.com>,
dri-devel@...ts.freedesktop.org,
Dave Stevenson <dave.stevenson@...pberrypi.com>,
linux-kernel@...r.kernel.org,
Geert Uytterhoeven <geert@...ux-m68k.org>,
Noralf Trønnes <noralf@...nnes.org>
Subject: Re: [PATCH v6 16/23] drm/probe-helper: Provide a TV get_modes helper
Den 26.10.2022 17.33, skrev maxime@...no.tech:
> Most of the TV connectors will need a similar get_modes implementation
> that will, depending on the drivers' capabilities, register the 480i and
> 576i modes.
>
> That implementation will also need to set the preferred flag and order
> the modes based on the driver and users preferrence.
>
> This is especially important to guarantee that a userspace stack such as
> Xorg can start and pick up the preferred mode while maintaining a
> working output.
>
> Signed-off-by: Maxime Ripard <maxime@...no.tech>
>
> ---
> Changes in v6:
> - New patch
> ---
> drivers/gpu/drm/drm_probe_helper.c | 97 ++++++++++++++++++++++++++++++++++++++
> include/drm/drm_probe_helper.h | 1 +
> 2 files changed, 98 insertions(+)
>
> diff --git a/drivers/gpu/drm/drm_probe_helper.c b/drivers/gpu/drm/drm_probe_helper.c
> index 69b0b2b9cc1c..4a60575f5c66 100644
> --- a/drivers/gpu/drm/drm_probe_helper.c
> +++ b/drivers/gpu/drm/drm_probe_helper.c
> @@ -1147,3 +1147,100 @@ int drm_connector_helper_get_modes(struct drm_connector *connector)
> return count;
> }
> EXPORT_SYMBOL(drm_connector_helper_get_modes);
> +
> +static bool tv_mode_supported(struct drm_connector *connector,
> + enum drm_connector_tv_mode mode)
> +{
> + struct drm_device *dev = connector->dev;
> + struct drm_property *property = dev->mode_config.tv_mode_property;
> +
Superfluous linebreak
> + unsigned int i;
> +
> + for (i = 0; i < property->num_values; i++)
> + if (property->values[i] == mode)
> + return true;
> +
> + return false;
> +}
> +
> +/**
> + * drm_connector_helper_tv_get_modes - Fills the modes availables to a TV connector
availables -> available
> + * @connector: The connector
> + *
> + * Fills the available modes for a TV connector based on the supported
> + * TV modes, and the default mode expressed by the kernel command line.
> + *
> + * This can be used as the default TV connector helper .get_modes() hook
> + * if the driver does not need any special processing.
> + *
> + * Returns:
> + * The number of modes added to the connector.
> + */
> +int drm_connector_helper_tv_get_modes(struct drm_connector *connector)
> +{
> + struct drm_device *dev = connector->dev;
> + struct drm_cmdline_mode *cmdline = &connector->cmdline_mode;
> + struct drm_display_mode *tv_modes[2] = {};
> + struct drm_display_mode *mode;
> + unsigned int first_mode_idx;
> + unsigned int count = 0;
> + uint64_t default_mode;
> + int ret;
> +
> + if (!dev->mode_config.tv_mode_property)
> + return 0;
> +
> + if (tv_mode_supported(connector, DRM_MODE_TV_MODE_NTSC) ||
> + tv_mode_supported(connector, DRM_MODE_TV_MODE_NTSC_443) ||
> + tv_mode_supported(connector, DRM_MODE_TV_MODE_NTSC_J) ||
> + tv_mode_supported(connector, DRM_MODE_TV_MODE_PAL_M)) {
> + mode = drm_mode_analog_ntsc_480i(connector->dev);
Nit: You can use the dev variable here and below.
> + if (!mode)
> + return 0;
> +
> + tv_modes[count++] = mode;
> + }
> +
> + if (tv_mode_supported(connector, DRM_MODE_TV_MODE_PAL) ||
> + tv_mode_supported(connector, DRM_MODE_TV_MODE_PAL_N) ||
> + tv_mode_supported(connector, DRM_MODE_TV_MODE_SECAM)) {
> + mode = drm_mode_analog_pal_576i(connector->dev);
> + if (!mode)
> + return 0;
You leak the ntsc mode when returning (possibly).
> +
> + tv_modes[count++] = mode;
> + }
> +
Maybe check for count being zero here?
> + if (count == 1) {
> + mode->type |= DRM_MODE_TYPE_PREFERRED;
> + drm_mode_probed_add(connector, mode);
> + return count;
> + }
> +
> + ret = drm_object_property_get_default_value(&connector->base,
> + dev->mode_config.tv_mode_property,
> + &default_mode);
> + if (ret)
> + return 0;
You leak both modes when returning here. Maybe move this up before
allocation to simplify error handling.
> +
> + if (cmdline->tv_mode_specified)
> + default_mode = cmdline->tv_mode;
I realised that we don't verify tv_mode coming from the command line,
not here and not in the reset helper. Should we do that? A driver should
be programmed defensively to handle an illegal/unsupported value, but it
doesn't feel right to allow an illegal enum value coming through the
core/helpers.
> +
> + if ((default_mode == DRM_MODE_TV_MODE_NTSC) ||
> + (default_mode == DRM_MODE_TV_MODE_NTSC_443) ||
> + (default_mode == DRM_MODE_TV_MODE_NTSC_J) ||
> + (default_mode == DRM_MODE_TV_MODE_PAL_M))
> + first_mode_idx = 0;
> + else
> + first_mode_idx = 1;
> +
> + mode = tv_modes[first_mode_idx];
> + mode->type |= DRM_MODE_TYPE_PREFERRED;
> + drm_mode_probed_add(connector, mode);
> +
> + mode = first_mode_idx ? tv_modes[0] : tv_modes[1];
> + drm_mode_probed_add(connector, mode);
> +
> + return count;
> +}
> +EXPORT_SYMBOL(drm_connector_helper_tv_get_modes);
I know this is not expensive, but you're looping over the property
values 7 times. An alternative solution is to rebuild the supported bitmask:
int drm_connector_helper_tv_get_modes(struct drm_connector *connector)
{
...
unsigned int ntsc_modes = BIT(DRM_MODE_TV_MODE_NTSC) |
BIT(DRM_MODE_TV_MODE_NTSC_443) |
BIT(DRM_MODE_TV_MODE_NTSC_J) |
BIT(DRM_MODE_TV_MODE_PAL_M);
unsigned int pal_modes = BIT(DRM_MODE_TV_MODE_PAL) |
BIT(DRM_MODE_TV_MODE_PAL_N) |
BIT(DRM_MODE_TV_MODE_SECAM);
unsigned int supported_tv_modes = 0;
...
for (i = 0; i < property->num_values; i++)
supported_tv_modes |= BIT(property->values[i]);
if (supported_tv_modes & ntsc_modes)
...
if (supported_tv_modes & pal_modes)
...
if (BIT(default_mode) & ntsc_modes)
first_mode_idx = 0;
else
first_mode_idx = 1;
Up to you if you want to do this.
Noralf.
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