Re: [PATCH 01/12 v2] Platform: add a dev_groups pointer to struct platform_driver

Richard Gong
2019-07-25T18:49:30Z

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
>>>> <gregkh@linuxfoundation.org> 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
>>>>>> <gregkh@linuxfoundation.org> 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
>>>>>>>> <gregkh@linuxfoundation.org> 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(). To align
with Dmitry's patch, I also change my code to use the new dev_groups
pointer in the struct of device_driver.

My changes are below,

diff --git a/include/linux/device.h b/include/linux/device.h
index 6717ade..9207aea3 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -296,6 +296,7 @@ struct device_driver {
int (*suspend) (struct device *dev, pm_message_t state);
int (*resume) (struct device *dev);
const struct attribute_group **groups;
+ const struct attribute_group **dev_groups;

const struct dev_pm_ops *pm;

diff --git a/drivers/base/dd.c b/drivers/base/dd.c
index 994a907..a91e69f 100644
--- a/drivers/base/dd.c
+++ b/drivers/base/dd.c
@@ -554,9 +554,19 @@ static int really_probe(struct device *dev, struct
device_driver *drv)
goto probe_failed;
}

+ if (drv->dev_groups) {
+ if (device_add_groups(dev, drv->dev_groups)) {
+ dev_err(dev, "device_add_groups(%s) failed\n",
+ dev_name(dev));
+ goto dev_groups_failed;
+ }
+ }
+
if (test_remove) {
test_remove = false;

+ device_remove_groups(dev, drv->dev_groups);
+
if (dev->bus->remove)
dev->bus->remove(dev);
else if (drv->remove)
@@ -584,6 +594,12 @@ static int really_probe(struct device *dev, struct
device_driver *drv)
drv->bus->name, __func__, dev_name(dev), drv->name);
goto done;

+dev_groups_failed:
+ if (dev->bus->remove)
+ dev->bus->remove(dev);
+ else if (drv->remove)
+ drv->remove(dev);
+
probe_failed:
if (dev->bus)
blocking_notifier_call_chain(&dev->bus->p->bus_notifier,
@@ -1114,6 +1130,8 @@ static void __device_release_driver(struct device
*dev, struct device *parent)

pm_runtime_put_sync(dev);

+ device_remove_groups(dev, drv->dev_groups);
+
if (dev->bus && dev->bus->remove)
dev->bus->remove(dev);
else if (drv->remove)

diff --git a/drivers/firmware/stratix10-rsu.c
b/drivers/firmware/stratix10-rsu.c
index 98d8030..93b44e9 100644
--- a/drivers/firmware/stratix10-rsu.c
+++ b/drivers/firmware/stratix10-rsu.c
@@ -391,9 +391,9 @@ static int stratix10_rsu_remove(struct
platform_device *pdev)
static struct platform_driver stratix10_rsu_driver = {
.probe = stratix10_rsu_probe,
.remove = stratix10_rsu_remove,
.driver = {
.name = "stratix10-rsu",
+ .dev_groups = rsu_groups,
},
};

Regards,
Richard

>>
>> diff --git a/drivers/base/dd.c b/drivers/base/dd.c
>> index 0df9b4461766..61d9d650d890 100644
>> --- a/drivers/base/dd.c
>> +++ b/drivers/base/dd.c
>> @@ -515,9 +515,17 @@ static int really_probe(struct device *dev, struct device_driver *drv)
>> goto probe_failed;
>> }
>>
>> + if (device_add_groups(dev, drv->dev_groups)) {
>> + printk(KERN_ERR "%s: device_add_groups(%s) failed\n",
>> + __func__, dev_name(dev));
>
> dev_err() of course :)
>
> thanks for the review, much appreciated.
>
> greg k-h
>