Messages in this thread | | | Date | Sat, 29 Aug 2015 02:53:30 -0700 | From | Guenter Roeck <> | Subject | Re: [PATCH] watchdog_dev: Use device tree alias for naming watchdogs |
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On 08/28/2015 02:58 PM, Justin Chen wrote: > Currently there is no way to easily differentiate multiple > watchdog devices. The watchdogs are named by the order they > are probed. > 1st probed watchdog: /dev/watchdog0 > 2nd probed watchdog: /dev/watchdog1 > ... > > This change uses the alias of the watchdog device node for > the name of the watchdog. > aliases { > watchdog0 = "/...../...." > watchdog3 = "/..../....." > watchdog2 = "/..../....." > ... > } > > This will translate to... > /dev/watchdog0 > /dev/watchdog3 > /dev/watchdog2 > > Signed-off-by: Justin Chen <justinpopo6@gmail.com>
Interesting idea. Checking through other subsystems, many others do the same, so it makes sense to use that mechanism.
However, the id assignment should be in the calling code, in __watchdog_register_device, to avoid that another id, possibly conflicting, is assigned through the ida mechanism.
This is a bit more complicated than it looks like to ensure correct id assignment. Have a look into the i2c code to see how it is handled. Essentially we must pass the requested number to ida_simple_get().
Thanks, Guenter
> --- > drivers/watchdog/watchdog_dev.c | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c > index 6aaefba..52b1f0b 100644 > --- a/drivers/watchdog/watchdog_dev.c > +++ b/drivers/watchdog/watchdog_dev.c > @@ -41,6 +41,7 @@ > #include <linux/miscdevice.h> /* For handling misc devices */ > #include <linux/init.h> /* For __init/__exit/... */ > #include <linux/uaccess.h> /* For copy_to_user/put_user/... */ > +#include <linux/of.h> > > #include "watchdog_core.h" > > @@ -522,7 +523,13 @@ static struct miscdevice watchdog_miscdev = { > > int watchdog_dev_register(struct watchdog_device *watchdog) > { > - int err, devno; > + int err, devno, ret; > + > + if (watchdog->parent) { > + ret = of_alias_get_id(watchdog->parent->of_node, "watchdog"); > + if (ret >= 0) > + watchdog->id = ret; > + } > > if (watchdog->id == 0) { > old_wdd = watchdog; >
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