[<prev] [next>] [<thread-prev] [day] [month] [year] [list]
Message-ID: <20150315142759.GA22313@katana>
Date: Sun, 15 Mar 2015 15:27:59 +0100
From: Wolfram Sang <wsa@...-dreams.de>
To: Antonio Borneo <borneo.antonio@...il.com>
Cc: Benjamin Tissoires <benjamin.tissoires@...hat.com>,
Jiri Kosina <jkosina@...e.cz>,
linux-input <linux-input@...r.kernel.org>,
Jonathan Cameron <jic23@...nel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
linux-i2c@...r.kernel.org
Subject: Re: [PATCH] hid: cp2112: support i2c_transfer() when num > 1
> >> 1) in few kernel drivers i2c_transfer() has been used to
> >> simplify the code by replacing a sequence of i2c_master_send()
> >> and i2c_master_recv(), e.g. in i2c-hid.c and iio subsystem.
> >> Those drivers will fail if used with current cp2112 driver.
> >
> > I see two options for those:
> >
> > 1) revert the simplifications and sacrifice a bit of performance
> > to support the widest number of adapters
> > 2) use the quirk infrastructure from above to query the
> > quirks of the adapter to chose between fast or compatible
>
> Could this be an extension of your quirks?
> I mean, moving in i2c-core the switch between fast or compatible?
> The caller should only state if combined transfer is strictly required
> by the device on I2C bus.
I'd first need some arguments that this is not micro-optimization :)
> I have check most of the I2C adapter drivers. At least for the 6
> drivers above, reading the code I don't see anything that implements
> the repeated start. But I do not have the HW to run a test.
> It's definitively possible I misread them.
I can't guarantee this in detail. The qup driver is quite new, so I am
quite sure I asked for that. However, I don't know for the USB drivers,
I have to trust the driver authors. puv3? Predates me, uh, let's not
talk about it... The main thing still stands: If they send stop after
each msg, this is a bug.
> >> To fix 1) and considering 2), rewrite i2c_transfer() in case
> >> of num > 1 as a loop of non-combined i2c transactions.
> >
> > For the above reasons, NAK.
>
> Ok, agree to drop this patch.
Thanks.
> > And why is this driver in hid? This is clearly an I2C master driver?
>
> Actually it should be a MFD, since it implements I2C/SMB master and GPIO.
> It uses HID over USB, that is probably the reason it is here.
Yup, from what I glimpsed, it should really be an MFD driver.
Download attachment "signature.asc" of type "application/pgp-signature" (820 bytes)
Powered by blists - more mailing lists