From: Tushar Behera <tushar.behera@xxxxxxxxxx>
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 <tushar.behera@xxxxxxxxxx>
[cernekee: fix checkpatch warnings]
Signed-off-by: Kevin Cernekee <cernekee@xxxxxxxxx>
---
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
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