From: Stephan Gerhold <stephan@gerhold.net>
To: Andi Shyti <andi@etezian.org>
Cc: Linux Input <linux-input@vger.kernel.org>,
Seung-Woo Kim <sw0312.kim@samsung.com>,
Dmitry Torokhov <dmitry.torokhov@gmail.com>,
Joonyoung Shim <jy0922.shim@samsung.com>
Subject: Re: [PATCH v2 1/2] Input: mms114 - use smbus functions whenever possible
Date: Mon, 21 Oct 2019 18:26:32 +0200 [thread overview]
Message-ID: <20191021162632.GA83253@gerhold.net> (raw)
In-Reply-To: <20191021154105.GC2278@jack.zhora.eu>
On Mon, Oct 21, 2019 at 06:41:05PM +0300, Andi Shyti wrote:
> Hi Stephan,
>
> > Not sure if you saw my comment regarding your patch [1],
> > so I'll just repeat it properly inline here:
> >
> > [1]: https://patchwork.kernel.org/patch/11178515/#22927311
> >
> > On Sun, Oct 20, 2019 at 11:28:55PM +0300, Andi Shyti wrote:
> > > The exchange of data to and from the mms114 touchscreen never
> > > exceeds 256 bytes. In the worst case it goes up to 80 bytes in
> > > the interrupt handler while reading the events.
> > >
> >
> > i2c_smbus_read_i2c_block_data() is actually limited to
> > I2C_SMBUS_BLOCK_MAX = 32.
>
> oh sorry, I don't know how I slipped on this.
>
> But this means that the i2c in the kernel is wrong (or outdated),
> smbus specifies 256 bytes of data[*]. I might have relied on the
> specification more than the code.
>
> I guess SMBUS needs some update.
You are right. It seems like that part of the specification was changed
with SMBus version 3.0 [1]:
D.6 255 Bytes in Process Call:
The maximum number of bytes allowed in the Block Write-Block Read
Process Call (Section 6.5.8) was increased from 32 to 255.
[1]: http://www.smbus.org/specs/SMBus_3_0_20141220.pdf
next prev parent reply other threads:[~2019-10-21 16:26 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-20 20:28 [PATCH v2 0/2] Use smbus functions to communicate through i2c Andi Shyti
2019-10-20 20:28 ` [PATCH v2 1/2] Input: mms114 - use smbus functions whenever possible Andi Shyti
2019-10-21 9:34 ` Stephan Gerhold
2019-10-21 15:41 ` Andi Shyti
2019-10-21 16:26 ` Stephan Gerhold [this message]
2019-10-21 16:39 ` Andi Shyti
2019-10-22 3:21 ` Dmitry Torokhov
2019-10-22 11:18 ` Andi Shyti
2019-11-18 13:32 ` Stephan Gerhold
2019-12-04 16:47 ` Stephan Gerhold
2019-10-20 20:28 ` [PATCH v2 2/2] Input: mms114 - get read of custm i2c read/write functions Andi Shyti
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