| Message ID | 20250525104022.1326997-1-mitltlatltl@gmail.com |
|---|---|
| State | New |
| Headers | show |
| Series | [RFC,1/2] backlight: Rename duplicated devices to support dual-backlight setups | expand |
On Sun, 25 May 2025, Pengyu Luo <mitltlatltl@gmail.com> wrote: > When registering a backlight device, if a device with the same name > already exists, append "-secondary" to the new device's name. This is > useful for platforms with dual backlight drivers (e.g. some panels use > dual ktz8866), where both instances need to coexist. > > For now, only one secondary instance is supported. If more instances > are needed, this logic can be extended with auto-increment or a more > flexible naming scheme. I think for both patches you should consider adding a new interface for creating dual backlight scenarios. For example, this patch turns a driver error (registering two or more backlights with the same name) into a special use case, patch 2 magically connecting the two, and hiding the problem. With i915, you could have multiple devices, each with multiple independent panels with independent backlights. I think accidentally trying to register more than one backlight with the same name should remain an error, *unless* you want the special case of combined backlights. Similarly, what if you encounter a device with two panels, and two *independent* ktz8866? Please be explicit rather than implicit. BR, Jani. > > Suggested-by: Daniel Thompson <danielt@kernel.org> > Signed-off-by: Pengyu Luo <mitltlatltl@gmail.com> > --- > drivers/video/backlight/backlight.c | 20 ++++++++++++++++++-- > 1 file changed, 18 insertions(+), 2 deletions(-) > > diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c > index 9dc93c5e4..991702f5d 100644 > --- a/drivers/video/backlight/backlight.c > +++ b/drivers/video/backlight/backlight.c > @@ -365,7 +365,8 @@ struct backlight_device *backlight_device_register(const char *name, > struct device *parent, void *devdata, const struct backlight_ops *ops, > const struct backlight_properties *props) > { > - struct backlight_device *new_bd; > + struct backlight_device *new_bd, *prev_bd; > + const char *new_name = NULL; > int rc; > > pr_debug("backlight_device_register: name=%s\n", name); > @@ -377,10 +378,23 @@ struct backlight_device *backlight_device_register(const char *name, > mutex_init(&new_bd->update_lock); > mutex_init(&new_bd->ops_lock); > > + /* > + * If there is an instance with the same name already, then rename it. > + * We also can use an auto-increment field, but it seems that there is > + * no triple or quad case. > + */ > + prev_bd = backlight_device_get_by_name(name); > + if (!IS_ERR_OR_NULL(prev_bd)) { > + 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; > new_bd->dev.parent = parent; > new_bd->dev.release = bl_device_release; > - dev_set_name(&new_bd->dev, "%s", name); > + dev_set_name(&new_bd->dev, "%s", new_name ? new_name : name); > dev_set_drvdata(&new_bd->dev, devdata); > > /* Set default properties */ > @@ -414,6 +428,8 @@ struct backlight_device *backlight_device_register(const char *name, > list_add(&new_bd->entry, &backlight_dev_list); > mutex_unlock(&backlight_dev_list_mutex); > > + kfree(new_name); > + > return new_bd; > } > EXPORT_SYMBOL(backlight_device_register);
diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c index 9dc93c5e4..991702f5d 100644 --- a/drivers/video/backlight/backlight.c +++ b/drivers/video/backlight/backlight.c @@ -365,7 +365,8 @@ struct backlight_device *backlight_device_register(const char *name, struct device *parent, void *devdata, const struct backlight_ops *ops, const struct backlight_properties *props) { - struct backlight_device *new_bd; + struct backlight_device *new_bd, *prev_bd; + const char *new_name = NULL; int rc; pr_debug("backlight_device_register: name=%s\n", name); @@ -377,10 +378,23 @@ struct backlight_device *backlight_device_register(const char *name, mutex_init(&new_bd->update_lock); mutex_init(&new_bd->ops_lock); + /* + * If there is an instance with the same name already, then rename it. + * We also can use an auto-increment field, but it seems that there is + * no triple or quad case. + */ + prev_bd = backlight_device_get_by_name(name); + if (!IS_ERR_OR_NULL(prev_bd)) { + 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; new_bd->dev.parent = parent; new_bd->dev.release = bl_device_release; - dev_set_name(&new_bd->dev, "%s", name); + dev_set_name(&new_bd->dev, "%s", new_name ? new_name : name); dev_set_drvdata(&new_bd->dev, devdata); /* Set default properties */ @@ -414,6 +428,8 @@ struct backlight_device *backlight_device_register(const char *name, list_add(&new_bd->entry, &backlight_dev_list); mutex_unlock(&backlight_dev_list_mutex); + kfree(new_name); + return new_bd; } EXPORT_SYMBOL(backlight_device_register);
When registering a backlight device, if a device with the same name already exists, append "-secondary" to the new device's name. This is useful for platforms with dual backlight drivers (e.g. some panels use dual ktz8866), where both instances need to coexist. For now, only one secondary instance is supported. If more instances are needed, this logic can be extended with auto-increment or a more flexible naming scheme. Suggested-by: Daniel Thompson <danielt@kernel.org> Signed-off-by: Pengyu Luo <mitltlatltl@gmail.com> --- drivers/video/backlight/backlight.c | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-)