From: Bartosz Golaszewski <bgolaszewski@baylibre.com>
To: Sakari Ailus <sakari.ailus@linux.intel.com>
Cc: linux-i2c <linux-i2c@vger.kernel.org>,
Wolfram Sang <wsa@the-dreams.de>,
"Rafael J. Wysocki" <rafael@kernel.org>,
linux-acpi@vger.kernel.org, Bingbu Cao <bingbu.cao@intel.com>,
linux-media <linux-media@vger.kernel.org>,
Chiranjeevi Rapolu <chiranjeevi.rapolu@intel.com>,
Hyungwoo Yang <hyungwoo.yang@intel.com>,
Arnd Bergmann <arnd@arndb.de>,
LKML <linux-kernel@vger.kernel.org>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Rajmohan Mani <rajmohan.mani@intel.com>,
Tomasz Figa <tfiga@chromium.org>
Subject: Re: [PATCH v4 5/6] at24: Support probing while off
Date: Thu, 12 Mar 2020 14:10:32 +0100 [thread overview]
Message-ID: <CAMpxmJVPTKW+sYSJ3dnfF8nLAOKEa4Ob7bpxG0KD3Tkdm+rtYw@mail.gmail.com> (raw)
In-Reply-To: <20200311085555.GH5379@paasikivi.fi.intel.com>
śr., 11 mar 2020 o 09:56 Sakari Ailus <sakari.ailus@linux.intel.com> napisał(a):
>
> Hi Bartosz,
>
> Thanks for the reply.
>
> On Wed, Jan 29, 2020 at 02:36:17PM +0100, Bartosz Golaszewski wrote:
> > wt., 21 sty 2020 o 14:41 Sakari Ailus <sakari.ailus@linux.intel.com> napisał(a):
> > >
> > > In certain use cases (where the chip is part of a camera module, and the
> > > camera module is wired together with a camera privacy LED), powering on
> > > the device during probe is undesirable. Add support for the at24 to
> > > execute probe while being powered off. For this to happen, a hint in form
> > > of a device property is required from the firmware.
> > >
> > > Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
> > > ---
> > > drivers/misc/eeprom/at24.c | 31 +++++++++++++++++++++----------
[snip!]
> > >
> > > static int at24_remove(struct i2c_client *client)
> > > {
> > > + bool low_power;
> > > +
> > > pm_runtime_disable(&client->dev);
> > > - pm_runtime_set_suspended(&client->dev);
> > > + low_power = acpi_dev_state_low_power(&client->dev);
> >
> > This is inconsistent. You define the low_power field in the context
> > structure (BTW the name low_power is a bit vague here - without
> > looking at its assignment it would make me think it's about something
> > battery-related, how about 'off_at_probe'?) and instead of reusing
>
> The field was called probe_powered_off in v1, but I changed it to
> probe_low_power (and renamed related functions etc.) based on review
> comments --- for the device may not be powered off actually.
>
But is it actually ever low-power? What are the possible logical
states of the device? If I understood correctly: it's either off or on
at probe - not actually low-power. Am I missing something? In your
cover letter you're writing: "These patches enable calling (and
finishing) a driver's probe function without powering on the
respective device on busses where the practice is to power on the
device for probe." To me there's no mention of a low-power state,
which makes the name 'probe_low_power' seem completely unrelated.
> > this field here, you call acpi_dev_state_low_power() again. Either
> > don't store the context for the life-time of the device if not
> > necessary or don't call acpi_dev_state_low_power() at remove, although
> > the commit message doesn't describe whether the latter is done on
> > purpose.
>
> Right. probe-low-power property has the same effect on remove for
> consistency, i.e. the device can remain in low power state during remove.
> This is documented in probe_low_power field documentation in the first
> patch.
>
Just please don't store any state if you're not using it outside of
the probe() function.
Bartosz
next prev parent reply other threads:[~2020-03-12 13:10 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-21 13:41 [PATCH v4 0/6] Support running driver's probe for a device powered off Sakari Ailus
2020-01-21 13:41 ` [PATCH v4 1/6] i2c: Allow driver to manage the device's power state during probe Sakari Ailus
2020-01-29 13:54 ` Bartosz Golaszewski
2020-03-23 21:36 ` Sakari Ailus
2020-01-21 13:41 ` [PATCH v4 2/6] ACPI: Add a convenience function to tell a device is in low power state Sakari Ailus
2020-01-21 16:07 ` Rafael J. Wysocki
2020-01-21 13:41 ` [PATCH v4 3/6] ov5670: Support probe whilst the device is in a " Sakari Ailus
2020-01-21 13:41 ` [PATCH v4 4/6] media: i2c: imx319: Support probe while the device is off Sakari Ailus
2020-01-21 13:41 ` [PATCH v4 5/6] at24: Support probing while off Sakari Ailus
2020-01-29 13:36 ` Bartosz Golaszewski
2020-03-11 8:55 ` Sakari Ailus
2020-03-12 13:10 ` Bartosz Golaszewski [this message]
2020-03-23 21:31 ` Sakari Ailus
2020-03-25 13:48 ` Bartosz Golaszewski
2020-08-10 8:25 ` Sakari Ailus
2020-08-10 18:12 ` Bartosz Golaszewski
2020-08-11 8:00 ` Sakari Ailus
2020-08-12 18:07 ` Bartosz Golaszewski
2020-08-12 19:25 ` Wolfram Sang
2020-08-12 19:33 ` Bartosz Golaszewski
2020-01-21 13:41 ` [PATCH v4 6/6] Documentation: ACPI: Document probe-low-power _DSD property Sakari Ailus
2020-01-21 16:09 ` Rafael J. Wysocki
2020-01-21 16:18 ` Sakari Ailus
2020-01-21 16:56 ` Rafael J. Wysocki
2020-01-21 16:58 ` Sakari Ailus
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