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Wysocki" , Andy Shevchenko , Mans Rullgard , Bartosz Golaszewski , Randy Dunlap Subject: Re: [PATCH 01/12 v2] Platform: add a dev_groups pointer to struct platform_driver Message-ID: <20190725191831.GB884@penguin> References: <20190704121143.GA5007@kroah.com> <20190706083251.GA9249@kroah.com> <20190706171948.GA23324@kroah.com> <20190719115220.GD20044@kroah.com> <20190720043857.GA14290@penguin> <20190725134411.GE11115@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Richard, On Thu, Jul 25, 2019 at 02:02:03PM -0500, Richard Gong wrote: > Hi Greg, > > On 7/25/19 8:44 AM, Greg Kroah-Hartman wrote: > > On Sat, Jul 20, 2019 at 07:38:57AM +0300, Dmitry Torokhov wrote: > > > On Fri, Jul 19, 2019 at 08:52:20PM +0900, Greg Kroah-Hartman wrote: > > > > On Sat, Jul 06, 2019 at 10:39:38AM -0700, Dmitry Torokhov wrote: > > > > > On Sat, Jul 6, 2019 at 10:19 AM Greg Kroah-Hartman > > > > > wrote: > > > > > > > > > > > > On Sat, Jul 06, 2019 at 10:04:39AM -0700, Dmitry Torokhov wrote: > > > > > > > Hi Greg, > > > > > > > > > > > > > > On Sat, Jul 6, 2019 at 1:32 AM Greg Kroah-Hartman > > > > > > > wrote: > > > > > > > > > > > > > > > > On Thu, Jul 04, 2019 at 02:17:22PM -0700, Dmitry Torokhov wrote: > > > > > > > > > Hi Greg, > > > > > > > > > > > > > > > > > > On Thu, Jul 4, 2019 at 5:15 AM Greg Kroah-Hartman > > > > > > > > > wrote: > > > > > > > > > > > > > > > > > > > > Platform drivers like to add sysfs groups to their device, but right now > > > > > > > > > > they have to do it "by hand". The driver core should handle this for > > > > > > > > > > them, but there is no way to get to the bus-default attribute groups as > > > > > > > > > > all platform devices are "special and unique" one-off drivers/devices. > > > > > > > > > > > > > > > > > > > > To combat this, add a dev_groups pointer to platform_driver which allows > > > > > > > > > > a platform driver to set up a list of default attributes that will be > > > > > > > > > > properly created and removed by the platform driver core when a probe() > > > > > > > > > > function is successful and removed right before the device is unbound. > > > > > > > > > > > > > > > > > > Why is this limited to platform bus? Drivers for other buses also > > > > > > > > > often want to augment list of their attributes during probe(). I'd > > > > > > > > > move it to generic probe handling. > > > > > > > > > > > > > > > > This is not limited to the platform at all, the driver core supports > > > > > > > > this for any bus type today, but it's then up to the bus-specific code > > > > > > > > to pass that on to the driver core. That's usually set for the > > > > > > > > bus-specific attributes that they want exposed for all devices of that > > > > > > > > bus type (see the bus_groups, dev_groups, and drv_groups pointers in > > > > > > > > struct bus_type). > > > > > > > > > > > > > > > > For the platform devices, the problem is that this is something that the > > > > > > > > individual drivers want after they bind to the device. And as all > > > > > > > > platform devices are "different" they can't be a "common" set of > > > > > > > > attributes, so they need to be created after the device is bound to the > > > > > > > > driver. > > > > > > > > > > > > > > I believe that your assertion that only platform devices want to > > > > > > > install custom attributes is incorrect. > > > > > > > > > > > > Sorry, I didn't mean to imply that only platform drivers want to do > > > > > > this, as you say, many other drivers do as well. > > > > > > > > > > > > > Drivers for devices attached > > > > > > > to serio, i2c, USB, spi, etc, etc, all have additional attributes: > > > > > > > > > > > > > > dtor@dtor-ws:~/kernel/work (master *)$ grep -l '\(i2c\|usb\|spi\)' > > > > > > > `git grep -l '\(device_add_group\|sysfs_create_group\)' -- drivers` | > > > > > > > wc -l > > > > > > > 170 > > > > > > > > > > > > > > I am pretty sure some of this count is false positives, but majority > > > > > > > is actually proper hits. > > > > > > > > > > > > Yeah, I know, we need to add this type of functionality to those busses > > > > > > as well. I don't see a way of doing it other than this bus-by-bus > > > > > > conversion, do you? > > > > > > > > > > Can't you push the **dev_groups from platform driver down to the > > > > > generic driver structure and handle them in driver_sysfs_add()? > > > > > > > > Sorry for the delay, got busy with the merge window... > > > > > > > > Anyway, no, we can't call this then, because driver_sysfs_add() is > > > > called before probe() is called. So if probe() fails, we don't bind the > > > > device to the driver. We also should not be creating sysfs files for a > > > > driver that has not had probe() called yet, as internal structures will > > > > not be set up at that time. > > > > > > Ah, yes, I got confused by the fact that driver_sysfs_remove is called > > > early. Anyway, I think you want something like this: > > > > Ah, nice, this looks good. Let me try this and see how it goes... > > > > I tried Dmitry's patch on Intel Stratix10 platform and it works. > > I added one minor change on the top of Dmitry's patch, since I think we need > add one additional check prior to device_add_groups(). sysfs_create_groups() returns success when NULL is passed, and device_add_groups() is a simple wrapper around it. If anything I'd prefer to codify the behavior of device_add_groups()/sysfs_create_groups() via comments rather than adding unneeded checks. Thanks. -- Dmitry