From: "Pali Rohár" <pali.rohar@gmail.com>
To: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Cc: "Benjamin Tissoires" <benjamin.tissoires@redhat.com>,
"Michał Kępień" <kernel@kempniu.pl>,
"Jean Delvare" <jdelvare@suse.com>,
"Wolfram Sang" <wsa@the-dreams.de>,
"Steven Honeyman" <stevenhoneyman@gmail.com>,
Valdis.Kletnieks@vt.edu,
"Jochen Eisinger" <jochen@penguin-breeder.org>,
"Gabriele Mazzotta" <gabriele.mzt@gmail.com>,
"Andy Lutomirski" <luto@kernel.org>,
Mario_Limonciello@dell.com, "Alex Hung" <alex.hung@canonical.com>,
"Takashi Iwai" <tiwai@suse.de>,
linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org,
platform-driver-x86@vger.kernel.org
Subject: Re: [PATCH] i2c: i801: Register optional lis3lv02d i2c device on Dell machines
Date: Tue, 3 Jan 2017 21:05:51 +0100 [thread overview]
Message-ID: <201701032105.51144@pali> (raw)
In-Reply-To: <20170103194812.GD16032@dtor-ws>
[-- Attachment #1: Type: Text/Plain, Size: 9473 bytes --]
On Tuesday 03 January 2017 20:48:12 Dmitry Torokhov wrote:
> On Tue, Jan 03, 2017 at 07:50:17PM +0100, Pali Rohár wrote:
> > On Tuesday 03 January 2017 19:38:43 Dmitry Torokhov wrote:
> > > On Tue, Jan 03, 2017 at 10:06:41AM +0100, Benjamin Tissoires
> > > wrote:
> > > > On Dec 29 2016 or thereabouts, Pali Rohár wrote:
> > > > > On Thursday 29 December 2016 22:09:32 Michał Kępień wrote:
> > > > > > > On Thursday 29 December 2016 14:47:19 Michał Kępień wrote:
> > > > > > > > > On Thursday 29 December 2016 09:29:36 Michał Kępień
> > > > > > > > > wrote:
> > > > > > > > > > > Dell platform team told us that some (DMI
> > > > > > > > > > > whitelisted) Dell Latitude machines have ST
> > > > > > > > > > > microelectronics accelerometer at i2c address
> > > > > > > > > > > 0x29. That i2c address is not specified in DMI
> > > > > > > > > > > or ACPI, so runtime detection without whitelist
> > > > > > > > > > > which is below is not possible.
> > > > > > > > > > >
> > > > > > > > > > > Presence of that ST microelectronics
> > > > > > > > > > > accelerometer is verified by existence of
> > > > > > > > > > > SMO88xx ACPI device which represent that
> > > > > > > > > > > accelerometer. Unfortunately without i2c
> > > > > > > > > > > address.
> > > > > > > > > >
> > > > > > > > > > This part of the commit message sounded a bit
> > > > > > > > > > confusing to me at first because there is already
> > > > > > > > > > an ACPI driver which handles SMO88xx
> > > > > > > > > >
> > > > > > > > > > devices (dell-smo8800). My understanding is that:
> > > > > > > > > > * the purpose of this patch is to expose a richer
> > > > > > > > > > interface (as
> > > > > > > > > >
> > > > > > > > > > provided by lis3lv02d) to these devices on some
> > > > > > > > > > machines,
> > > > > > > > > >
> > > > > > > > > > * on whitelisted machines, dell-smo8800 and
> > > > > > > > > > lis3lv02d can work
> > > > > > > > > >
> > > > > > > > > > simultaneously (even though dell-smo8800
> > > > > > > > > > effectively duplicates the work that lis3lv02d
> > > > > > > > > > does).
> > > > > > > > >
> > > > > > > > > No. dell-smo8800 reads from ACPI irq number and
> > > > > > > > > exports /dev/freefall device which notify userspace
> > > > > > > > > about falls. lis3lv02d is i2c driver which exports
> > > > > > > > > axes of accelerometer. Additionaly lis3lv02d can
> > > > > > > > > export also /dev/freefall if registerer of i2c
> > > > > > > > > device provides irq number -- which is not case of
> > > > > > > > > this patch.
> > > > > > > > >
> > > > > > > > > So both drivers are doing different things and both
> > > > > > > > > are useful.
> > > > > > > > >
> > > > > > > > > IIRC both dell-smo8800 and lis3lv02d represent one HW
> > > > > > > > > device (that ST microelectronics accelerometer) but
> > > > > > > > > due to complicated HW abstraction and layers on Dell
> > > > > > > > > laptops it is handled by two drivers, one ACPI and
> > > > > > > > > one i2c.
> > > > > > > > >
> > > > > > > > > Yes, in ideal world irq number should be passed to
> > > > > > > > > lis3lv02d driver and that would export whole device
> > > > > > > > > (with /dev/freefall too), but due to HW abstraction
> > > > > > > > > it is too much complicated...
> > > > > > > >
> > > > > > > > Why? AFAICT, all that is required to pass that IRQ
> > > > > > > > number all the way down to lis3lv02d is to set the irq
> > > > > > > > field of the struct i2c_board_info you are passing to
> > > > > > > > i2c_new_device(). And you can extract that IRQ number
> > > > > > > > e.g. in check_acpi_smo88xx_device(). However, you would
> > > > > > > > then need to make sure dell-smo8800 does not attempt to
> > > > > > > > request the same IRQ on whitelisted machines. This got
> > > > > > > > me thinking about a way to somehow incorporate your
> > > > > > > > changes into dell-smo8800 using Wolfram's bus_notifier
> > > > > > > > suggestion, but I do not have a working solution for
> > > > > > > > now. What is tempting about this approach is that you
> > > > > > > > would not have to scan the ACPI namespace in search of
> > > > > > > > SMO88xx devices, because smo8800_add() is
> > > > > > > > automatically called for them. However, I fear that
> > > > > > > > the resulting solution may be more complicated than
> > > > > > > > the one you submitted.
> > > > > > >
> > > > > > > Then we need to deal with lot of problems. Order of
> > > > > > > loading .ko modules is undefined. Binding devices to
> > > > > > > drivers registered by .ko module is also in "random"
> > > > > > > order. At any time any of those .ko module can be
> > > > > > > unloaded or at least device unbind (via sysfs) from
> > > > > > > driver... And there can be some pathological situation
> > > > > > > (thanks to adding ACPI layer as Andy pointed) that there
> > > > > > > will be more SMO88xx devices in ACPI. Plus you can
> > > > > > > compile kernel with and without those modules and also
> > > > > > > you can blacklist loading them (so compile time check is
> > > > > > > not enough). And still some correct message notifier
> > > > > > > must be used.
> > > > > > >
> > > > > > > I think such solution is much much more complicated,
> > > > > > > there are lot of combinations of kernel configuration
> > > > > > > and available dell devices...
> > > > > >
> > > > > > I tried a few more things, but ultimately failed to find a
> > > > > > nice way to implement this.
> > > > > >
> > > > > > Another issue popped up, though. Linus' master branch
> > > > > > contains a recent commit by Benjamin Tissoires (CC'ed),
> > > > > > 4d5538f5882a ("i2c: use an IRQ to report Host Notify
> > > > > > events, not alert") which breaks your patch. The reason
> > > > > > for that is that lis3lv02d relies on the i2c client's IRQ
> > > > > > being 0 to detect that it should not create /dev/freefall.
> > > > > > Benjamin's patch causes the Host Notify IRQ to be
> > > > > > assigned to the i2c client your patch creates, thus
> > > > > > causing lis3lv02d to create /dev/freefall, which in turn
> > > > > > conflicts with dell-smo8800 which is trying to create
> > > > > > /dev/freefall itself.
> > > > >
> > > > > So 4d5538f5882a is breaking lis3lv02d driver...
> > > >
> > > > Apologies for that.
> > > >
> > > > I could easily fix this by adding a kernel API to know whether
> > > > the provided irq is from Host Notify or if it was coming from
> > > > an actual declaration. However, I have no idea how many other
> > > > drivers would require this (hopefully only this one).
> > > >
> > > > One other solution would be to reserve the Host Notify IRQ and
> > > > let the actual drivers that need it to set it, but this was
> > > > not the best solution according to Dmitri. On my side, I am
> > > > not entirely against this given that it's a chip feature, so
> > > > the driver should be able to know that it's available.
> > > >
> > > > Dmitri, Wolfram, Jean, any preferences?
> > >
> > > I read this:
> > >
> > > "IIRC both dell-smo8800 and lis3lv02d represent one HW device
> > > (that ST microelectronics accelerometer) but due to complicated
> > > HW abstraction and layers on Dell laptops it is handled by two
> > > drivers, one ACPI and one i2c."
> > >
> > > and that is the core of the issue. You have 2 drivers fighting
> > > over the same device. Fix this and it will all work.
> >
> > With my current implementation (which I sent in this patch), they
> > are not fighting.
> >
> > dell-smo8800 exports /dev/freefall (and nothing more) and lis3lv02d
> > only accelerometer device as lis3lv02d driver does not get IRQ
> > number in platform data.
> >
> > > As far as I can see hp_accel instantiates lis3lv02d and accesses
> > > it via ACPI methods, can the same be done for Dell?
> >
> > No, Dell does not have any ACPI methods. And as I wrote in ACPI or
> > DMI is even not i2c address of device, so it needs to be specified
> > in code itself.
> >
> > Really there is no other way... :-(
>
> Sure there is:
>
> 1. dell-smo8800 instantiates I2C device as "dell-smo8800-accel".
> 2. dell-smo8800 provides read/write functions for lis3lv02d that
> simply forward requests to dell-smo8800-accel i2c client.
> 3. dell-smo8800 instantiates lis3lv02d instance like hp_accel does.
Sorry, but I do not understand how you mean it... Why to provides new
read/write i2c functions which are already implemented by i2c-i801 bus
and lis3lv02d i2c driver?
> Alternatively, can lis3lv02d be tasked to create /dev/freefall?
If i2c_board_info contains IRQ then lis3lv02d create /dev/freefall
device.
But... what is problem with current implementation? Accelerometer HW
provides two functions:
1) 3 axes reports
2) Disk freefall detection
And 1) is handled by i2c driver lis3lv02d and 2) is by dell-smo8800.
Both functions are independent here.
I think you just trying to complicate this situation even more to be
more complicated as currently is.
> Yet another option: can we add a new flag to i2c_board_info
> controlling whether we want to enable/disable wiring up host notify
> interrupt? Benjamin, is there anything "special" in RMI SMbus ACPI
> descriptors we could use?
>
> Thanks.
--
Pali Rohár
pali.rohar@gmail.com
[-- Attachment #2: This is a digitally signed message part. --]
[-- Type: application/pgp-signature, Size: 198 bytes --]
next prev parent reply other threads:[~2017-01-03 20:06 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-12-27 12:52 [PATCH] i2c: i801: Register optional lis3lv02d i2c device on Dell machines Pali Rohár
2016-12-27 13:43 ` Wolfram Sang
2016-12-27 13:51 ` Pali Rohár
2016-12-27 22:15 ` Andy Shevchenko
2016-12-27 22:41 ` Valdis.Kletnieks
2016-12-28 7:55 ` Andy Shevchenko
2016-12-28 9:05 ` Pali Rohár
2016-12-28 14:03 ` Wolfram Sang
2016-12-29 4:37 ` Valdis.Kletnieks
2016-12-28 8:38 ` Pali Rohár
2016-12-28 14:02 ` Wolfram Sang
2017-01-04 9:45 ` Jean Delvare
2016-12-29 8:29 ` Michał Kępień
2016-12-29 9:00 ` Pali Rohár
2016-12-29 13:47 ` Michał Kępień
2016-12-29 14:17 ` Pali Rohár
2016-12-29 21:09 ` Michał Kępień
2016-12-29 21:28 ` Pali Rohár
2017-01-03 9:06 ` Benjamin Tissoires
2017-01-03 9:23 ` Pali Rohár
2017-01-03 18:38 ` Dmitry Torokhov
2017-01-03 18:50 ` Pali Rohár
2017-01-03 18:58 ` Mario.Limonciello
2017-01-03 19:48 ` Dmitry Torokhov
2017-01-03 20:05 ` Pali Rohár [this message]
2017-01-03 20:24 ` Dmitry Torokhov
2017-01-03 20:39 ` Pali Rohár
2017-01-03 20:59 ` Dmitry Torokhov
2017-01-04 8:18 ` Pali Rohár
2017-01-04 9:05 ` Benjamin Tissoires
2017-01-04 9:18 ` Pali Rohár
2017-01-04 10:13 ` Benjamin Tissoires
2017-01-04 10:21 ` Pali Rohár
2017-01-04 10:32 ` Benjamin Tissoires
2017-01-04 11:22 ` Pali Rohár
2017-01-04 12:00 ` Pali Rohár
2017-01-04 13:02 ` Benjamin Tissoires
2017-01-04 16:06 ` Pali Rohár
2017-01-04 17:39 ` Benjamin Tissoires
2017-01-04 17:46 ` Wolfram Sang
2017-01-04 17:54 ` Dmitry Torokhov
2017-01-04 21:49 ` Benjamin Tissoires
2017-01-04 21:55 ` Dmitry Torokhov
2017-01-04 21:55 ` Wolfram Sang
2017-01-04 22:00 ` Dmitry Torokhov
2017-01-04 22:03 ` Dmitry Torokhov
2017-01-05 2:20 ` [PATCH] i2c: do not enable fall back to Host Notify by default kbuild test robot
2017-01-05 2:21 ` kbuild test robot
2017-01-05 8:54 ` [PATCH] i2c: i801: Register optional lis3lv02d i2c device on Dell machines Pali Rohár
2017-01-05 9:26 ` Benjamin Tissoires
2017-01-04 18:50 ` Jean Delvare
2017-01-04 9:53 ` Andy Shevchenko
2017-01-04 10:25 ` Benjamin Tissoires
2017-01-04 11:35 ` Pali Rohár
2017-01-04 12:33 ` Benjamin Tissoires
2017-01-03 21:29 ` Benjamin Tissoires
2017-01-04 6:36 ` Dmitry Torokhov
2017-01-04 9:13 ` Benjamin Tissoires
2017-01-04 9:25 ` Pali Rohár
2017-01-03 20:20 ` Andy Shevchenko
2017-01-04 10:18 ` Jean Delvare
2017-01-07 12:49 ` Wolfram Sang
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=201701032105.51144@pali \
--to=pali.rohar@gmail.com \
--cc=Mario_Limonciello@dell.com \
--cc=Valdis.Kletnieks@vt.edu \
--cc=alex.hung@canonical.com \
--cc=benjamin.tissoires@redhat.com \
--cc=dmitry.torokhov@gmail.com \
--cc=gabriele.mzt@gmail.com \
--cc=jdelvare@suse.com \
--cc=jochen@penguin-breeder.org \
--cc=kernel@kempniu.pl \
--cc=linux-i2c@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=luto@kernel.org \
--cc=platform-driver-x86@vger.kernel.org \
--cc=stevenhoneyman@gmail.com \
--cc=tiwai@suse.de \
--cc=wsa@the-dreams.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).