[PATCH/RFC 1/8] tty: Fallback to use dynamic major number
From: Kevin Cernekee <cernekee@gmail.com>
Date: 2014-11-12 08:46:26
Also in:
linux-devicetree, linux-mips
Subsystem:
the rest, tty layer and serial drivers · Maintainers:
Linus Torvalds, Greg Kroah-Hartman, Jiri Slaby
From: Tushar Behera <redacted> In a multi-platform scenario, the hard-coded major/minor numbers in serial drivers may conflict with each other. A typical scenario is observed with amba-pl011 and samsung-uart drivers, both of these drivers use same set of major/minor numbers. If both of these drivers are enabled, probe of samsung-uart driver fails because the desired node is busy. The issue is fixed by adding a fallback in driver core, so that we can use dynamic major number in case device node allocation fails for hard-coded major/minor number. Signed-off-by: Tushar Behera <redacted> [cernekee: fix checkpatch warnings] Signed-off-by: Kevin Cernekee <cernekee@gmail.com> --- drivers/tty/tty_io.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-)
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index 0508a1d..a6d4d9a 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c@@ -3365,6 +3365,22 @@ int tty_register_driver(struct tty_driver *driver) dev_t dev; struct device *d; + if (driver->major) { + dev = MKDEV(driver->major, driver->minor_start); + error = register_chrdev_region(dev, driver->num, driver->name); + /* In case of error, fall back to dynamic allocation */ + if (error < 0) { + pr_warn("Default device node (%d:%d) for %s is busy, using dynamic major number\n", + driver->major, driver->minor_start, + driver->name); + driver->major = 0; + } + } + + /* + * Don't replace the following check with an else to above if statement, + * as it may also be called as a fallback. + */ if (!driver->major) { error = alloc_chrdev_region(&dev, driver->minor_start, driver->num, driver->name);
@@ -3372,9 +3388,6 @@ int tty_register_driver(struct tty_driver *driver) driver->major = MAJOR(dev); driver->minor_start = MINOR(dev); } - } else { - dev = MKDEV(driver->major, driver->minor_start); - error = register_chrdev_region(dev, driver->num, driver->name); } if (error < 0) goto err;
--
2.1.1