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([144.202.86.13]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-742a96defa1sm15833363b3a.12.2025.05.25.03.40.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 25 May 2025 03:40:34 -0700 (PDT) From: Pengyu Luo To: Lee Jones , Daniel Thompson , Jingoo Han , Helge Deller Cc: dri-devel@lists.freedesktop.org, linux-fbdev@vger.kernel.org, linux-kernel@vger.kernel.org, Pengyu Luo Subject: [RFC PATCH 2/2] backlight: Improve support for dual backlight with primary/secondary linkage Date: Sun, 25 May 2025 18:40:22 +0800 Message-ID: <20250525104022.1326997-2-mitltlatltl@gmail.com> X-Mailer: git-send-email 2.49.0 In-Reply-To: <20250525104022.1326997-1-mitltlatltl@gmail.com> References: <20250525104022.1326997-1-mitltlatltl@gmail.com> Precedence: bulk X-Mailing-List: linux-fbdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 This patch enhances dual-backlight handling by explicitly linking primary and secondary backlight devices using new fields: - `is_secondary`: Marks if a device is secondary in a pair - `secondary`: Points to the associated secondary device (if any) - `primary`: Points to the primary device (for secondary devices) It also update `backlight_update_status()` to ensure that both primary and secondary devices are updated together during brightness changes. This provides a consistent update mechanism in dual-backlight case. Suggested-by: Daniel Thompson Signed-off-by: Pengyu Luo --- drivers/video/backlight/backlight.c | 9 +++++- include/linux/backlight.h | 50 +++++++++++++++++++++++++++-- 2 files changed, 56 insertions(+), 3 deletions(-) diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c index 991702f5d..2e7b179bc 100644 --- a/drivers/video/backlight/backlight.c +++ b/drivers/video/backlight/backlight.c @@ -388,7 +388,6 @@ struct backlight_device *backlight_device_register(const char *name, new_name = kasprintf(GFP_KERNEL, "%s-secondary", name); if (!new_name) return ERR_PTR(-ENOMEM); - put_device(&prev_bd->dev); } new_bd->dev.class = &backlight_class; @@ -428,6 +427,14 @@ struct backlight_device *backlight_device_register(const char *name, list_add(&new_bd->entry, &backlight_dev_list); mutex_unlock(&backlight_dev_list_mutex); + /* set them until the secondary device is available */ + if (prev_bd) { + prev_bd->secondary = new_bd; + new_bd->primary = prev_bd; + new_bd->is_secondary = true; + put_device(&prev_bd->dev); + } + kfree(new_name); return new_bd; diff --git a/include/linux/backlight.h b/include/linux/backlight.h index 10e626db7..cde992e10 100644 --- a/include/linux/backlight.h +++ b/include/linux/backlight.h @@ -291,13 +291,42 @@ struct backlight_device { * @use_count: The number of unblanked displays. */ int use_count; + + /** + * @is_secondary: Indicates whether this backlight device is secondary. + */ + bool is_secondary; + + /** + * @secondary: Pointer to the secondary backlight device. + */ + struct backlight_device *secondary; + + /** + * @primary: Pointer to the primary backlight device. + * + * Non-NULL only for secondary devices. + */ + struct backlight_device *primary; }; +static inline struct backlight_device * +to_primary_backlight_device(struct backlight_device *bd) +{ + return bd->is_secondary ? bd->primary : bd; +} + +static inline struct backlight_device * +to_secondary_backlight_device(struct backlight_device *bd) +{ + return bd->is_secondary ? bd : bd->secondary; +} + /** - * backlight_update_status - force an update of the backlight device status + * backlight_update_status_single - force an update of the backlight device status * @bd: the backlight device */ -static inline int backlight_update_status(struct backlight_device *bd) +static inline int backlight_update_status_single(struct backlight_device *bd) { int ret = -ENOENT; @@ -309,6 +338,23 @@ static inline int backlight_update_status(struct backlight_device *bd) return ret; } +/** + * backlight_update_status - update primary and secondary backlight devices + * @bd: the backlight device + */ +static inline int backlight_update_status(struct backlight_device *bd) +{ + struct backlight_device *primary = to_primary_backlight_device(bd); + struct backlight_device *secondary = to_secondary_backlight_device(bd); + int ret; + + ret = backlight_update_status_single(primary); + if (!secondary || ret) + return ret; + + return backlight_update_status_single(secondary); +} + /** * backlight_enable - Enable backlight * @bd: the backlight device to enable