git: cb603e3ea2d4 - releng/13.0 - backlight: Fix incr/decr with percent value of 0

[Emmanuel Vadot]

The branch releng/13.0 has been updated by manu:

URL: https://cgit.FreeBSD.org/src/commit/?id=cb603e3ea2d4f2fee8fa4e59bda7e27704b6899c

commit cb603e3ea2d4f2fee8fa4e59bda7e27704b6899c
Author:     David Schlachter <fbsd-bugzilla at schlachter.ca>
AuthorDate: 2021-03-03 07:57:35 +0000
Commit:     Emmanuel Vadot <manu at FreeBSD.org>
CommitDate: 2021-03-11 08:49:03 +0000

    backlight: Fix incr/decr with percent value of 0
    
    This now does nothing instead of incr/decr by 10%
    
    MFC After:    3 days
    PR:           253736
    Approved by:  re (gjb)
    
    (cherry picked from commit 3b005d51bd0fe4d8d19fb2df4d470b6e8baebf16)
    (cherry picked from commit 9ba393f2ca0fd561c1fbf96f38eb014d7f883381)
---
 usr.bin/backlight/backlight.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/usr.bin/backlight/backlight.c b/usr.bin/backlight/backlight.c
index 1dae0cfe5c62..9cf7a0912e95 100644
--- a/usr.bin/backlight/backlight.c
+++ b/usr.bin/backlight/backlight.c
@@ -98,7 +98,7 @@ main(int argc, char *argv[])
 		BACKLIGHTGETSTATUS,
 		BACKLIGHTUPDATESTATUS,
 		BACKLIGHTGETINFO};
-	long percent = 0;
+	long percent = -1;
 	const char *percent_error;
 	uint32_t i;
 	bool setname;
@@ -188,15 +188,20 @@ main(int argc, char *argv[])
 		}
 		break;
 	case BACKLIGHT_SET_BRIGHTNESS:
+		if (percent == -1)
+			usage();
 		props.brightness = percent;
 		if (ioctl(fd, BACKLIGHTUPDATESTATUS, &props) == -1)
 			errx(1, "Cannot update the backlight device");
 		break;
 	case BACKLIGHT_INCR:
 	case BACKLIGHT_DECR:
+		if (percent == 0)
+			/* Avoid any ioctl if we don't have anything to do */
+			break;
 		if (ioctl(fd, BACKLIGHTGETSTATUS, &props) == -1)
 			errx(1, "Cannot query the backlight device");
-		percent = percent == 0 ? 10 : percent;
+		percent = percent == -1 ? 10 : percent;
 		percent = action == BACKLIGHT_INCR ? percent : -percent;
 		props.brightness += percent;
 		if ((int)props.brightness < 0)