Another round of cosmetic updates here, this should address everything
from the last round.
arm64: topology: Implement basic CPU topology support
arm64: topology: Add support for topology DT bindings
arm64: topology: Tell the scheduler about the relative
arm64: topology: Provide relative power numbers for cores
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(a)linaro.org>
---
Initial approach to fix this problem was by forcing samsung-uart driver
to use dynamic major number, but it was rejected [1] because of possible
user-space breakage. Current approach falls back to dynamic major
number as a fallback in case of failure.
[1] https://lkml.org/lkml/2013/12/27/2
Can I get an Acked-by/Reviewed-by before I send this to lkml?
Changes for V2:
* Added warning message in case major number is getting orverriden
drivers/tty/tty_io.c | 21 ++++++++++++++++++---
1 file changed, 18 insertions(+), 3 deletions(-)
diff --git a/drivers/tty/tty_io.c b/drivers/tty/tty_io.c
index c74a00a..ff4aada 100644
--- a/drivers/tty/tty_io.c
+++ b/drivers/tty/tty_io.c
@@ -3341,6 +3341,24 @@ 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) {
+ printk(KERN_WARNING
+ "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);
@@ -3348,9 +3366,6 @@ 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;
--
1.7.9.5
Another round of minor tweaks
- Remove some problematic and controversial prints
- Pass cluster_id around as a pointer
- Move slab.h further back in the series
arm64: topology: Implement basic CPU topology support
arm64: topology: Add support for topology DT bindings
arm64: topology: Tell the scheduler about the relative
arm64: topology: Provide relative power numbers for cores
