From 3ba5c78fe7c5d60edae0c47361f191d40c5c1cf0 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Jean-Fran=C3=A7ois=20Lessard?= Date: Thu, 18 Sep 2025 08:13:15 -0400 Subject: [PATCH] auxdisplay: linedisp: support attribute attachment to auxdisplay devices MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Enable linedisp library integration into existing kernel devices (like LED class) to provide a uniform 7-segment userspace API without creating separate child devices, meeting the consistent interface while maintaining coherent device hierarchies. This allows uniform 7-segment API across all drivers while solving device proliferation and fragmented userspace interfaces. The sysfs attributes appear in one of the two locations depending on usage: 1. On linedisp.N child devices (legacy linedisp_register()) 2. On the parent auxdisplay device (new linedisp_attach()) Functionality is identical in both modes. Existing consumers of linedisp_register() are unaffected. The new API enables drivers like TM16XX to integrate 7-segment display functionality seamlessly within their LED class device hierarchy. Signed-off-by: Jean-François Lessard Signed-off-by: Andy Shevchenko --- drivers/auxdisplay/line-display.c | 180 +++++++++++++++++++++++++++++- drivers/auxdisplay/line-display.h | 4 + 2 files changed, 178 insertions(+), 6 deletions(-) diff --git a/drivers/auxdisplay/line-display.c b/drivers/auxdisplay/line-display.c index 7f3e53e2847bb..4e22373fcc1a9 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 @@ -31,9 +34,80 @@ #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) { - return container_of(dev, struct linedisp, 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) @@ -348,6 +422,90 @@ static int linedisp_init_map(struct linedisp *linedisp) #define LINEDISP_INIT_TEXT "Linux " UTS_RELEASE " " #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 @@ -355,6 +513,11 @@ static int linedisp_init_map(struct linedisp *linedisp) * @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, @@ -390,19 +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: @@ -419,6 +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 4348d7a2f69ad..36853b6397115 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); -- 2.47.3