From: David Hsu <davidhsu@google.com>
To: Thierry Reding <thierry.reding@gmail.com>
Cc: Greg KH <gregkh@linuxfoundation.org>,
linux-pwm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] pwm: Create device class for pwm channels
Date: Wed, 15 Jun 2016 16:52:56 -0700 [thread overview]
Message-ID: <CAH7o3i6o2489ArgLRjhgv6uS+=RFq-dby9zc9vSMfDiQ62o86g@mail.gmail.com> (raw)
In-Reply-To: <20160615143720.GA23483@ulmo.ba.sec>
On Wed, Jun 15, 2016 at 7:37 AM, Thierry Reding
<thierry.reding@gmail.com> wrote:
> On Tue, Jun 14, 2016 at 07:12:04PM -0700, Greg KH wrote:
>> From: David Hsu <davidhsu@google.com>
>>
>> Pwm channels don't send uevents when exported, this change adds the
>> channels to a pwm class and set their device type to pwm_channel so
>> uevents are sent.
>>
>> To do this properly, the device names need to change to uniquely
>> identify a channel. This change is from pwmN to pwm-(chip->base):N
>>
>> Signed-off-by: David Hsu <davidhsu@google.com>
>> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
>> ---
>> Documentation/pwm.txt | 6 ++++--
>> drivers/pwm/sysfs.c | 15 ++++++++++++---
>> 2 files changed, 16 insertions(+), 5 deletions(-)
>>
>> Note, this patch came from David with his work on a system that has
>> dynamic PWM devices and channels, and we needed some way to tell
>> userspace what is going on when they are added or removed. If anyone
>> knows any other way of doing this that does not involve changing the pwm
>> names, please let us know.
>
> Is it truly PWM channels that dynamically appear and disappear? I'd be
> interested in how that's achieved, because there are probably other
> issues that will manifest if you do that. Do you have a pointer to the
> work that David's been undertaking? Generally some more context on the
> use-case would be helpful here.
Only PWM devices are dynamic, the number of channels exposed by
devices do not change after they've been added to the system.
>
> Also I'd prefer if this avoided using chip->base here, because it exists
> purely for legacy purposes and is supposed to go away eventually.
>
> Thierry
Would using dev_name(parent) be an acceptable alternative?
Thanks,
David
next prev parent reply other threads:[~2016-06-15 23:53 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-06-15 2:12 [PATCH] pwm: Create device class for pwm channels Greg KH
2016-06-15 14:37 ` Thierry Reding
2016-06-15 23:52 ` David Hsu [this message]
2016-06-24 20:54 ` David Hsu
2016-07-11 9:39 ` Thierry Reding
2016-07-12 1:25 ` David Hsu
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