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Date:   Fri, 29 Jul 2022 17:03:02 +0200
From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Cc:     alsa-devel@alsa-project.org, linux-kernel@vger.kernel.org,
        Vinod Koul <vkoul@kernel.org>,
        Sanyog Kale <sanyog.r.kale@intel.com>,
        Bard Liao <yung-chuan.liao@linux.intel.com>
Subject: Re: [PATCH 2/5] soundwire: sysfs: cleanup the logic for creating the
 dp0 sysfs attributes
Message-ID: <YuP2pjhyKTTfpXQq@kroah.com>
References: <20220729135041.2285908-1-gregkh@linuxfoundation.org>
 <20220729135041.2285908-2-gregkh@linuxfoundation.org>
 <9365e038-2146-98f8-f989-02827f221c34@linux.intel.com>
 <YuP0Ffs3G7ZBR0AC@kroah.com>
 <cfacb124-a9ff-0a93-8f92-93d164b15966@linux.intel.com>
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On Fri, Jul 29, 2022 at 09:57:52AM -0500, Pierre-Louis Bossart wrote:
> 
> 
> On 7/29/22 09:52, Greg Kroah-Hartman wrote:
> > On Fri, Jul 29, 2022 at 09:46:26AM -0500, Pierre-Louis Bossart wrote:
> >>
> >>
> >> On 7/29/22 08:50, Greg Kroah-Hartman wrote:
> >>> There's no need to special-case the dp0 sysfs attributes, the
> >>> is_visible() callback in the attribute group can handle that for us, so
> >>> add that and add it to the attribute group list making the logic simpler
> >>> overall.
> >>>
> >>> This is a step on the way to moving all of the sysfs attribute handling
> >>> into the default driver core attribute group logic so that the soundwire
> >>> core does not have to do any of it manually.
> >>>
> >>> Cc: Vinod Koul <vkoul@kernel.org>
> >>> Cc: Bard Liao <yung-chuan.liao@linux.intel.com>
> >>> Cc: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
> >>> Cc: Sanyog Kale <sanyog.r.kale@intel.com>
> >>> Cc: alsa-devel@alsa-project.org
> >>> Cc: linux-kernel@vger.kernel.org
> >>> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> >>> ---
> >>>  drivers/soundwire/sysfs_slave.c | 18 ++++++++++++------
> >>>  1 file changed, 12 insertions(+), 6 deletions(-)
> >>>
> >>> diff --git a/drivers/soundwire/sysfs_slave.c b/drivers/soundwire/sysfs_slave.c
> >>> index 83e3f6cc3250..3723333a5c2b 100644
> >>> --- a/drivers/soundwire/sysfs_slave.c
> >>> +++ b/drivers/soundwire/sysfs_slave.c
> >>> @@ -174,6 +174,16 @@ static ssize_t words_show(struct device *dev,
> >>>  }
> >>>  static DEVICE_ATTR_RO(words);
> >>>  
> >>> +static umode_t dp0_is_visible(struct kobject *kobj, struct attribute *attr,
> >>> +			      int n)
> >>> +{
> >>> +	struct sdw_slave *slave = dev_to_sdw_dev(kobj_to_dev(kobj));
> >>> +
> >>> +	if (slave->prop.dp0_prop)
> >>> +		return attr->mode;
> >>> +	return 0;
> >>> +}
> >>
> >> This changes the results slightly by creating an empty 'dp0' directory
> >> with no attributes inside.
> >>
> >> Before:
> >>
> >> [root@fedora ~]# cd /sys/bus/soundwire/devices/sdw:3:025d:0714:01
> >> [root@fedora sdw:3:025d:0714:01]# ls dp0
> >> ls: cannot access 'dp0': No such file or directory
> >>
> >> After:
> >> [root@fedora sdw:3:025d:0714:01]# ls dp0
> > 
> > That should be fine, tools should just be looking for the attributes,
> > not the existance of a directory, right?
> 
> The idea what that we would only expose ports that actually exist.
> That's helpful information anyone with a basic knowledge of the
> SoundWire specification would understand.

Is "dp0" a port?  If so, why isn't it a real device?

> The attributes are really details that few people/applications would
> understand, and unfortunately the information reported in DSDT is more
> often than not complete garbage.

I don't understand what DSDT is, or how it is relevant here :(

thanks,

greg k-h