At Wed, 28 Jan 2015 14:28:51 -0800, Greg Kroah-Hartman wrote: > > On Wed, Jan 28, 2015 at 11:18:57PM +0100, Takashi Iwai wrote: > > At Wed, 28 Jan 2015 13:34:21 -0800, > > Greg Kroah-Hartman wrote: > > > > > > On Wed, Jan 28, 2015 at 10:26:28PM +0100, Takashi Iwai wrote: > > > > At Wed, 28 Jan 2015 13:05:47 -0800, > > > > Greg Kroah-Hartman wrote: > > > > > > > > > > On Wed, Jan 28, 2015 at 09:46:12PM +0100, Takashi Iwai wrote: > > > > > > Hi, > > > > > > > > > > > > this is a simple patch to add device_create_files() and > > > > > > device_remove_files() to replace multiple device_create_file() or > > > > > > _remove() calls with a single shot with the device_attr list. > > > > > > > > > > > > It's basically just a clean up, but also helps to simplify the error > > > > > > handling a lot in many existing codes since the function itself does > > > > > > rollback at error. > > > > > > > > > > > > The series contains a patch to apply these to drivers/base/node.c. > > > > > > I have lots of patches (up to 30) to use these in the whole tree, > > > > > > but > > > > > > maybe it'd be easier too apply once after this stuff is merged at > > > > > > first. It's just a cleanup so no urgent task, after all. > > > > > > > > > > I'd like to some day be able to drop device_create_file entirely, as > > > > > it > > > > > is almost always used in a racy way (but not always, so we can't get > > > > > rid > > > > > of it today.) > > > > > > > > > > A driver should be using an attribute group and be created/registered > > > > > with it if they want any files associated with it, so giving people > > > > > the > > > > > ability to add large numbers of files all at once seems like the wrong > > > > > thing to do :) > > > > > > > > Well, through the glance over many codes using device_create_file(), > > > > I think the problem of the attribute group is that there is little > > > > help for generating the entries dynamically. For example, if you have > > > > two groups you want to enable conditionally, what would be the best > > > > way to implement? > > > > > > Use the is_visable() function callback, that's what it is there for. > > > > But if the entries are determined dynamically? Selecting the enabled > > elements from the static list is one way, it'd work in many cases, but > > it's not always the most straightforward way. It often would be > > easier to build up the list dynamically. > > Do you have an example of this? Wouldn't it be the same thing to list > them all in an attribute group, but only say "this is valid" in the > is_visable() callback for those that would have been built up > dynamically?
One common scene is the case where a device has already the static group defined in the core helper module while a driver wants to put additional sysfs entries on it. A complex case is something in drivers/leds/trigger/ledtrig-*.c. Another interesting example is drivers/regulator/core.c. It creates a bunch of various sysfs files depending on the client's ops presence. It might be implemented via is_visible, but then it'd become more lengthy (too many small callback functions). Also, multiple drivers seem calling device_create_file() from the array of attributes in a loop. One reason might be that it's easier to write for a bunch of entries, without defining many piece of structs. An example is found in drivers/gpu/drm/drm_sysfs.c. > > What if having a link to the chained group for appending entries > > dynamically? Just a wild idea, but it might make things easier. > > We have the ability to pass a group list pointer to device_create > already, and the attribute pointer is a list of groups as well, how can > we change this to be "easier"? I guess the order is the problem. In many cases, you know the additional entries only after the device creation. The device creation is often done by a helper code. So the driver has no control to it, just gets the resultant device. thanks, Takashi -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
