From 9870334f486763b2d93ced6f9dcd5d009fe6ec80 Mon Sep 17 00:00:00 2001 From: =?utf8?q?Jean-Fran=C3=A7ois=20Lessard?= Date: Thu, 18 Sep 2025 08:13:13 -0400 Subject: [PATCH] auxdisplay: linedisp: display static message when length <= display size MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Currently, when a message shorter than the display size is written, the content wraps around (e.g., "123" on a 4-digit display shows "1231") without scrolling, which is confusing and unintuitive. Change behavior to display short messages statically with space padding (e.g. "123 ") while only scrolling messages longer than the display width. This provides more natural behavior that aligns with user expectations and current linedisp_display() kernel-doc. The scroll logic is also consolidated into a helper function for clarity. No API changes are introduced. Signed-off-by: Jean-François Lessard Signed-off-by: Andy Shevchenko --- drivers/auxdisplay/line-display.c | 30 +++++++++++++++++++++--------- 1 file changed, 21 insertions(+), 9 deletions(-) diff --git a/drivers/auxdisplay/line-display.c b/drivers/auxdisplay/line-display.c index e44341b1ea220..73e4e77ea4f9b 100644 --- a/drivers/auxdisplay/line-display.c +++ b/drivers/auxdisplay/line-display.c @@ -36,6 +36,11 @@ static struct linedisp *to_linedisp(struct device *dev) return container_of(dev, struct linedisp, dev); } +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 @@ -67,8 +72,7 @@ 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); } /** @@ -118,8 +122,16 @@ 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; } @@ -186,12 +198,12 @@ 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; } -- 2.47.3