From: Samuel Ortiz <sameo@linux.intel.com>
To: Rabin VINCENT <rabin.vincent@stericsson.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
STEricsson_nomadik_linux <STEricsson_nomadik_linux@list.st.com>,
Linus WALLEIJ <linus.walleij@stericsson.com>,
"l.fu@pengutronix.de" <l.fu@pengutronix.de>
Subject: Re: [PATCHv2 1/3] mfd: add STMPE I/O Expander support
Date: Tue, 29 Jun 2010 17:33:27 +0200 [thread overview]
Message-ID: <20100629153326.GA4752@sortiz-mobl> (raw)
In-Reply-To: <20100629031324.GA6430@bnru02.bnr.st.com>
Hi Rabin,
On Tue, Jun 29, 2010 at 08:43:26AM +0530, Rabin VINCENT wrote:
> Hi Samuel,
>
> On Mon, Jun 28, 2010 at 01:55:16 +0200, Samuel Ortiz wrote:
> > On Tue, Jun 22, 2010 at 07:25:27PM +0530, Rabin Vincent wrote:
> > > +int stmpe_reg_read(struct stmpe *stmpe, u8 reg)
> > > +{
> > > + int ret;
> > > +
> > > + ret = i2c_smbus_read_byte_data(stmpe->i2c, reg);
> > > + if (ret < 0)
> > > + dev_err(stmpe->dev, "failed to read reg %#x: %d\n",
> > > + reg, ret);
> > > +
> > > + dev_vdbg(stmpe->dev, "rd: reg %#x => data %#x\n", reg, ret);
> > > +
> > > + return ret;
> > > +}
> > > +EXPORT_SYMBOL(stmpe_reg_read);
> > I think your locking is broken here.
> > If your exporting this routine (and the next ones below), you'd better make
> > sure you're under stmpe->lock for the stmpe register concurrent access.
>
> stmpe_reg_read() and stmpe_reg_write() are just a call to one
> i2c_smbus_* function, and the I2C core takes a bus_lock internally
> preventing concurrent accesses.
>
> The only place where the I2C core locking is not sufficient is the
> read/modify/write sequence, and we provide stmpe_set_bits() for that,
> which takes a lock. If someone uses reg_read()/reg_write() sequences on
> registers where they should be using set_bits(), adding extra locking in
> reg_read()/reg_write() will not provide any additional safeguard.
>
> The same scheme is used by adp5520.
>
> Could you please explain why more locking is needed?
Without the extra locking, there's nothing preventing me from writing to a
register while you're in the middle of a stmpe_set_bits() call.
> > > +/**
> > > + * stmpe_block_write() - write multiple stmpe registers
> > > + * @stmpe: device to write to
> > > + * @reg: first register
> > > + * @length: number of registers
> > > + * @values: values to write
> > > + */
> > > +int stmpe_block_write(struct stmpe *stmpe, u8 reg, u8 length,
> > > + const u8 *values)
> > > +{
> > > + int ret;
> > > +
> > > + dev_vdbg(stmpe->dev, "wr: regs %#x (%d)\n", reg, length);
> > > +#ifdef VERBOSE_DEBUG
> > > + print_hex_dump_bytes("stmpe wr: ", dump_prefix_offset, values, length);
> > > +#endif
> > I don't really enjoy this part for 2 reasons:
> > - You should use a less generic ifdef switch, prefixed with STMPE_ for
> > example.
>
> The dev_vdbg() in the previous line is activated via VERBOSE_DEBUG, so
> the idea was to have this dump use the same config.
Ah, I didnt realize VERBOSE_DEBUG was defined from device.h. Should have
grepped for it in your patch, sorry.
I would still like it to be part of your header file though.
> I'll fix it as your recommended, though. Will fix your other comments too.
Thanks in advance.
Cheers,
Samuel.
> Rabin
--
Intel Open Source Technology Centre
http://oss.intel.com/
next prev parent reply other threads:[~2010-06-29 15:33 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-05-31 12:17 [PATCH 1/3] mfd: add STMPExxxx I/O Expander support Rabin Vincent
2010-05-31 12:17 ` [PATCH 2/3] gpio: add STMPExxxx GPIO driver Rabin Vincent
2010-05-31 12:17 ` [PATCH 3/3] input: add STMPExxxx keypad driver Rabin Vincent
2010-06-01 22:16 ` Dmitry Torokhov
2010-06-02 13:56 ` Rabin VINCENT
2010-06-02 16:05 ` Dmitry Torokhov
2010-06-18 23:42 ` [PATCH 1/3] mfd: add STMPExxxx I/O Expander support Samuel Ortiz
2010-06-19 13:50 ` Luotao Fu
2010-06-21 13:33 ` Rabin VINCENT
2010-06-21 15:45 ` Luotao Fu
2010-06-22 13:55 ` [PATCHv2 1/3] mfd: add STMPE " Rabin Vincent
2010-06-27 23:55 ` Samuel Ortiz
2010-06-29 3:13 ` Rabin VINCENT
2010-06-29 15:33 ` Samuel Ortiz [this message]
2010-07-01 12:00 ` [PATCHv3 " Rabin Vincent
2010-07-01 12:34 ` Luotao Fu
2010-07-02 11:22 ` [PATCHv4 " Rabin Vincent
2010-07-02 15:31 ` Samuel Ortiz
2010-07-02 11:22 ` [PATCHv4 2/3] gpio: add STMPE GPIO driver Rabin Vincent
2010-07-02 11:22 ` [PATCHv4 3/3] input: add STMPE keypad driver Rabin Vincent
2010-07-02 12:10 ` [RESEND] [PATCH V8] input: STMPE touch controller support Luotao Fu
2010-07-05 14:53 ` Samuel Ortiz
2010-07-01 12:00 ` [PATCHv3 2/3] gpio: add STMPE GPIO driver Rabin Vincent
2010-07-01 12:29 ` Luotao Fu
2010-07-01 12:00 ` [PATCHv3 3/3] input: add STMPE keypad driver Rabin Vincent
2010-06-22 13:55 ` [PATCHv2 2/3] gpio: add STMPE GPIO driver Rabin Vincent
2010-06-22 13:55 ` [PATCHv2 3/3] input: add STMPE keypad driver Rabin Vincent
2010-06-22 13:56 ` [PATCH 1/3] mfd: add STMPExxxx I/O Expander support Rabin VINCENT
2010-06-24 11:13 ` mfd: STMPExxxx fixes and touch screen support Luotao Fu
2010-06-24 11:13 ` [PATCH 1/6] gpio/stmpe-gpio: set GPIO alternate function while requesting Luotao Fu
2010-06-24 12:43 ` Rabin VINCENT
2010-06-24 11:13 ` [PATCH 2/6] gpio/stmpe-gpio: fix set direction input Luotao Fu
2010-06-24 12:03 ` Rabin VINCENT
2010-06-24 11:13 ` [PATCH 3/6] mfd/stmpexxx: add touchscreen platform data Luotao Fu
2010-06-24 11:13 ` [PATCH 4/6] mfd/stmpexxx: change touchscreen irq Luotao Fu
2010-06-24 13:09 ` Rabin VINCENT
2010-06-24 13:17 ` Luotao Fu
2010-06-24 11:13 ` [PATCH 5/6] mfd/stmpexxx: fix stmpe811 enable hook Luotao Fu
2010-06-24 12:11 ` Rabin VINCENT
2010-06-24 12:32 ` Luotao Fu
2010-06-24 12:47 ` [PATCH 5/6 V3] " Luotao Fu
2010-06-24 13:05 ` Rabin VINCENT
2010-06-24 11:13 ` [PATCH 6/6 V4] input: STMPE touch controller support Luotao Fu
2010-06-24 12:27 ` [PATCH 5/6 V2] mfd/stmpexxx: fix stmpe811 enable hook Luotao Fu
2010-06-24 12:35 ` Rabin VINCENT
2010-06-24 12:46 ` Luotao Fu
2010-06-24 12:28 ` [PATCH 6/6 V5] input: STMPE touch controller support Luotao Fu
2010-06-24 14:26 ` [PATCH 5/5] " Luotao Fu
2010-06-24 16:24 ` Dmitry Torokhov
2010-06-24 16:57 ` Luotao Fu
2010-06-25 8:37 ` [PATCH 5/5 V7] " Luotao Fu
2010-06-25 9:11 ` Dmitry Torokhov
2010-06-25 9:32 ` Luotao Fu
2010-06-27 21:24 ` Samuel Ortiz
2010-06-25 9:34 ` [PATCH 5/5 V8] " Luotao Fu
2010-06-24 12:31 ` [PATCH 6/6 V4] " Rabin VINCENT
2010-06-24 12:42 ` Luotao Fu
2010-06-24 13:01 ` Rabin VINCENT
2010-06-24 13:11 ` Luotao Fu
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