diff --git a/Documentation/ABI/testing/sysfs-auxdisplay-linedisp b/Documentation/ABI/testing/sysfs-auxdisplay-linedisp new file mode 100644 index 0000000..55f1b55 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-auxdisplay-linedisp @@ -0,0 +1,90 @@ +What: /sys/.../message +Date: October 2021 +KernelVersion: 5.16 +Description: + Controls the text message displayed on character line displays. + + Reading returns the current message with a trailing newline. + Writing updates the displayed message. Messages longer than the + display width will automatically scroll. Trailing newlines in + input are automatically trimmed. + + Writing an empty string clears the display. + + Example: + echo "Hello World" > message + cat message # Returns "Hello World\n" + +What: /sys/.../num_chars +Date: November 2025 +KernelVersion: 6.18 +Contact: Jean-François Lessard +Description: + Read-only attribute showing the character width capacity of + the line display device. Messages longer than this will scroll. + + Example: + cat num_chars # Returns "16\n" for 16-char display + +What: /sys/.../scroll_step_ms +Date: October 2021 +KernelVersion: 5.16 +Description: + Controls the scrolling speed for messages longer than the display + width, specified in milliseconds per scroll step. + + Setting to 0 disables scrolling. Default is 500ms. + + Example: + echo "250" > scroll_step_ms # 4Hz scrolling + cat scroll_step_ms # Returns "250\n" + +What: /sys/.../map_seg7 +Date: January 2024 +KernelVersion: 6.9 +Description: + Read/write binary blob representing the ASCII-to-7-segment + display conversion table used by the linedisp driver, as defined + by struct seg7_conversion_map in . + + Only visible on displays with 7-segment capability. + + This attribute is not human-readable. Writes must match the + struct size exactly, else -EINVAL is returned; reads return the + entire mapping as a binary blob. + + This interface and its implementation match existing conventions + used in segment-mapped display drivers since 2005. + + ABI note: This style of binary sysfs attribute *is an exception* + to current "one value per file, text only" sysfs rules, for + historical compatibility and driver uniformity. New drivers are + discouraged from introducing additional binary sysfs ABIs. + + Reference interface guidance: + - include/uapi/linux/map_to_7segment.h + +What: /sys/.../map_seg14 +Date: January 2024 +KernelVersion: 6.9 +Description: + Read/write binary blob representing the ASCII-to-14-segment + display conversion table used by the linedisp driver, as defined + by struct seg14_conversion_map in . + + Only visible on displays with 14-segment capability. + + This attribute is not human-readable. Writes must match the + struct size exactly, else -EINVAL is returned; reads return the + entire mapping as a binary blob. + + This interface and its implementation match existing conventions + used by segment-mapped display drivers since 2005. + + ABI note: This style of binary sysfs attribute *is an exception* + to current "one value per file, text only" sysfs rules, for + historical compatibility and driver uniformity. New drivers are + discouraged from introducing additional binary sysfs ABIs. + + Reference interface guidance: + - include/uapi/linux/map_to_14segment.h diff --git a/drivers/auxdisplay/line-display.c b/drivers/auxdisplay/line-display.c index 8590a4c..4e22373 100644 --- a/drivers/auxdisplay/line-display.c +++ b/drivers/auxdisplay/line-display.c @@ -6,20 +6,23 @@ * Author: Paul Burton * * Copyright (C) 2021 Glider bv + * Copyright (C) 2025 Jean-François Lessard */ #ifndef CONFIG_PANEL_BOOT_MESSAGE #include #endif -#include +#include #include #include #include #include #include +#include #include #include +#include #include #include #include @@ -32,6 +35,87 @@ #define DEFAULT_SCROLL_RATE (HZ / 2) /** + * struct linedisp_attachment - Holds the device to linedisp mapping + * @list: List entry for the linedisp_attachments list + * @device: Pointer to the device where linedisp attributes are added + * @linedisp: Pointer to the linedisp mapped to the device + * @direct: true for directly attached device using linedisp_attach(), + * false for child registered device using linedisp_register() + */ +struct linedisp_attachment { + struct list_head list; + struct device *device; + struct linedisp *linedisp; + bool direct; +}; + +static LIST_HEAD(linedisp_attachments); +static DEFINE_SPINLOCK(linedisp_attachments_lock); + +static int create_attachment(struct device *dev, struct linedisp *linedisp, bool direct) +{ + struct linedisp_attachment *attachment; + + attachment = kzalloc(sizeof(*attachment), GFP_KERNEL); + if (!attachment) + return -ENOMEM; + + attachment->device = dev; + attachment->linedisp = linedisp; + attachment->direct = direct; + + guard(spinlock)(&linedisp_attachments_lock); + list_add(&attachment->list, &linedisp_attachments); + + return 0; +} + +static struct linedisp *delete_attachment(struct device *dev, bool direct) +{ + struct linedisp_attachment *attachment; + struct linedisp *linedisp; + + guard(spinlock)(&linedisp_attachments_lock); + + list_for_each_entry(attachment, &linedisp_attachments, list) { + if (attachment->device == dev && + attachment->direct == direct) + break; + } + + if (list_entry_is_head(attachment, &linedisp_attachments, list)) + return NULL; + + linedisp = attachment->linedisp; + list_del(&attachment->list); + kfree(attachment); + + return linedisp; +} + +static struct linedisp *to_linedisp(struct device *dev) +{ + struct linedisp_attachment *attachment; + + guard(spinlock)(&linedisp_attachments_lock); + + list_for_each_entry(attachment, &linedisp_attachments, list) { + if (attachment->device == dev) + break; + } + + if (list_entry_is_head(attachment, &linedisp_attachments, list)) + return NULL; + + return attachment->linedisp; +} + +static inline bool should_scroll(struct linedisp *linedisp) +{ + return linedisp->message_len > linedisp->num_chars && linedisp->scroll_rate; +} + +/** * linedisp_scroll() - scroll the display by a character * @t: really a pointer to the private data structure * @@ -62,8 +146,7 @@ static void linedisp_scroll(struct timer_list *t) linedisp->scroll_pos %= linedisp->message_len; /* rearm the timer */ - if (linedisp->message_len > num_chars && linedisp->scroll_rate) - mod_timer(&linedisp->timer, jiffies + linedisp->scroll_rate); + mod_timer(&linedisp->timer, jiffies + linedisp->scroll_rate); } /** @@ -113,8 +196,16 @@ static int linedisp_display(struct linedisp *linedisp, const char *msg, linedisp->message_len = count; linedisp->scroll_pos = 0; - /* update the display */ - linedisp_scroll(&linedisp->timer); + if (should_scroll(linedisp)) { + /* display scrolling message */ + linedisp_scroll(&linedisp->timer); + } else { + /* display static message */ + memset(linedisp->buf, ' ', linedisp->num_chars); + memcpy(linedisp->buf, linedisp->message, + umin(linedisp->num_chars, linedisp->message_len)); + linedisp->ops->update(linedisp); + } return 0; } @@ -133,7 +224,7 @@ static int linedisp_display(struct linedisp *linedisp, const char *msg, static ssize_t message_show(struct device *dev, struct device_attribute *attr, char *buf) { - struct linedisp *linedisp = container_of(dev, struct linedisp, dev); + struct linedisp *linedisp = to_linedisp(dev); return sysfs_emit(buf, "%s\n", linedisp->message); } @@ -152,7 +243,7 @@ static ssize_t message_show(struct device *dev, struct device_attribute *attr, static ssize_t message_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count) { - struct linedisp *linedisp = container_of(dev, struct linedisp, dev); + struct linedisp *linedisp = to_linedisp(dev); int err; err = linedisp_display(linedisp, buf, count); @@ -161,10 +252,20 @@ static ssize_t message_store(struct device *dev, struct device_attribute *attr, static DEVICE_ATTR_RW(message); +static ssize_t num_chars_show(struct device *dev, struct device_attribute *attr, + char *buf) +{ + struct linedisp *linedisp = to_linedisp(dev); + + return sysfs_emit(buf, "%u\n", linedisp->num_chars); +} + +static DEVICE_ATTR_RO(num_chars); + static ssize_t scroll_step_ms_show(struct device *dev, struct device_attribute *attr, char *buf) { - struct linedisp *linedisp = container_of(dev, struct linedisp, dev); + struct linedisp *linedisp = to_linedisp(dev); return sysfs_emit(buf, "%u\n", jiffies_to_msecs(linedisp->scroll_rate)); } @@ -173,7 +274,7 @@ static ssize_t scroll_step_ms_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count) { - struct linedisp *linedisp = container_of(dev, struct linedisp, dev); + struct linedisp *linedisp = to_linedisp(dev); unsigned int ms; int err; @@ -181,12 +282,12 @@ static ssize_t scroll_step_ms_store(struct device *dev, if (err) return err; + timer_delete_sync(&linedisp->timer); + linedisp->scroll_rate = msecs_to_jiffies(ms); - if (linedisp->message && linedisp->message_len > linedisp->num_chars) { - timer_delete_sync(&linedisp->timer); - if (linedisp->scroll_rate) - linedisp_scroll(&linedisp->timer); - } + + if (should_scroll(linedisp)) + linedisp_scroll(&linedisp->timer); return count; } @@ -195,7 +296,7 @@ static DEVICE_ATTR_RW(scroll_step_ms); static ssize_t map_seg_show(struct device *dev, struct device_attribute *attr, char *buf) { - struct linedisp *linedisp = container_of(dev, struct linedisp, dev); + struct linedisp *linedisp = to_linedisp(dev); struct linedisp_map *map = linedisp->map; memcpy(buf, &map->map, map->size); @@ -205,7 +306,7 @@ static ssize_t map_seg_show(struct device *dev, struct device_attribute *attr, c static ssize_t map_seg_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count) { - struct linedisp *linedisp = container_of(dev, struct linedisp, dev); + struct linedisp *linedisp = to_linedisp(dev); struct linedisp_map *map = linedisp->map; if (count != map->size) @@ -223,6 +324,7 @@ static DEVICE_ATTR(map_seg14, 0644, map_seg_show, map_seg_store); static struct attribute *linedisp_attrs[] = { &dev_attr_message.attr, + &dev_attr_num_chars.attr, &dev_attr_scroll_step_ms.attr, &dev_attr_map_seg7.attr, &dev_attr_map_seg14.attr, @@ -232,7 +334,7 @@ static struct attribute *linedisp_attrs[] = { static umode_t linedisp_attr_is_visible(struct kobject *kobj, struct attribute *attr, int n) { struct device *dev = kobj_to_dev(kobj); - struct linedisp *linedisp = container_of(dev, struct linedisp, dev); + struct linedisp *linedisp = to_linedisp(dev); struct linedisp_map *map = linedisp->map; umode_t mode = attr->mode; @@ -263,7 +365,7 @@ static DEFINE_IDA(linedisp_id); static void linedisp_release(struct device *dev) { - struct linedisp *linedisp = container_of(dev, struct linedisp, dev); + struct linedisp *linedisp = to_linedisp(dev); kfree(linedisp->map); kfree(linedisp->message); @@ -321,12 +423,101 @@ static int linedisp_init_map(struct linedisp *linedisp) #endif /** + * linedisp_attach - attach a character line display + * @linedisp: pointer to character line display structure + * @dev: pointer of the device to attach to + * @num_chars: the number of characters that can be displayed + * @ops: character line display operations + * + * Directly attach the line-display sysfs attributes to the passed device. + * The caller is responsible for calling linedisp_detach() to release resources + * after use. + * + * Return: zero on success, else a negative error code. + */ +int linedisp_attach(struct linedisp *linedisp, struct device *dev, + unsigned int num_chars, const struct linedisp_ops *ops) +{ + int err; + + memset(linedisp, 0, sizeof(*linedisp)); + linedisp->ops = ops; + linedisp->num_chars = num_chars; + linedisp->scroll_rate = DEFAULT_SCROLL_RATE; + + linedisp->buf = kzalloc(linedisp->num_chars, GFP_KERNEL); + if (!linedisp->buf) + return -ENOMEM; + + /* initialise a character mapping, if required */ + err = linedisp_init_map(linedisp); + if (err) + goto out_free_buf; + + /* initialise a timer for scrolling the message */ + timer_setup(&linedisp->timer, linedisp_scroll, 0); + + err = create_attachment(dev, linedisp, true); + if (err) + goto out_del_timer; + + /* display a default message */ + err = linedisp_display(linedisp, LINEDISP_INIT_TEXT, -1); + if (err) + goto out_del_attach; + + /* add attribute groups to target device */ + err = device_add_groups(dev, linedisp_groups); + if (err) + goto out_del_attach; + + return 0; + +out_del_attach: + delete_attachment(dev, true); +out_del_timer: + timer_delete_sync(&linedisp->timer); +out_free_buf: + kfree(linedisp->buf); + return err; +} +EXPORT_SYMBOL_NS_GPL(linedisp_attach, "LINEDISP"); + +/** + * linedisp_detach - detach a character line display + * @dev: pointer of the device to detach from, that was previously + * attached with linedisp_attach() + */ +void linedisp_detach(struct device *dev) +{ + struct linedisp *linedisp; + + linedisp = delete_attachment(dev, true); + if (!linedisp) + return; + + timer_delete_sync(&linedisp->timer); + + device_remove_groups(dev, linedisp_groups); + + kfree(linedisp->map); + kfree(linedisp->message); + kfree(linedisp->buf); +} +EXPORT_SYMBOL_NS_GPL(linedisp_detach, "LINEDISP"); + +/** * linedisp_register - register a character line display * @linedisp: pointer to character line display structure * @parent: parent device * @num_chars: the number of characters that can be displayed * @ops: character line display operations * + * Register the line-display sysfs attributes to a new device named + * "linedisp.N" added to the passed parent device. + * The caller is responsible for calling linedisp_unregister() to release + * resources after use. + * * Return: zero on success, else a negative error code. */ int linedisp_register(struct linedisp *linedisp, struct device *parent, @@ -362,19 +553,23 @@ int linedisp_register(struct linedisp *linedisp, struct device *parent, /* initialise a timer for scrolling the message */ timer_setup(&linedisp->timer, linedisp_scroll, 0); - err = device_add(&linedisp->dev); + err = create_attachment(&linedisp->dev, linedisp, false); if (err) goto out_del_timer; /* display a default message */ err = linedisp_display(linedisp, LINEDISP_INIT_TEXT, -1); if (err) - goto out_del_dev; + goto out_del_attach; + + err = device_add(&linedisp->dev); + if (err) + goto out_del_attach; return 0; -out_del_dev: - device_del(&linedisp->dev); +out_del_attach: + delete_attachment(&linedisp->dev, false); out_del_timer: timer_delete_sync(&linedisp->timer); out_put_device: @@ -391,6 +586,7 @@ EXPORT_SYMBOL_NS_GPL(linedisp_register, "LINEDISP"); void linedisp_unregister(struct linedisp *linedisp) { device_del(&linedisp->dev); + delete_attachment(&linedisp->dev, false); timer_delete_sync(&linedisp->timer); put_device(&linedisp->dev); } diff --git a/drivers/auxdisplay/line-display.h b/drivers/auxdisplay/line-display.h index 4348d7a..36853b6 100644 --- a/drivers/auxdisplay/line-display.h +++ b/drivers/auxdisplay/line-display.h @@ -6,6 +6,7 @@ * Author: Paul Burton * * Copyright (C) 2021 Glider bv + * Copyright (C) 2025 Jean-François Lessard */ #ifndef _LINEDISP_H @@ -81,6 +82,9 @@ struct linedisp { unsigned int id; }; +int linedisp_attach(struct linedisp *linedisp, struct device *dev, + unsigned int num_chars, const struct linedisp_ops *ops); +void linedisp_detach(struct device *dev); int linedisp_register(struct linedisp *linedisp, struct device *parent, unsigned int num_chars, const struct linedisp_ops *ops); void linedisp_unregister(struct linedisp *linedisp);