From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Dmitry Torokhov" Subject: Re: [PATCH 2/3] Input/Touchscreen Driver: add support AD7877 touchscreen driver Date: Mon, 15 Oct 2007 13:33:31 -0400 Message-ID: References: <600D5CB4DFD93545BF61FF01473D11AC0F2B13C2@limkexm2.ad.analog.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <600D5CB4DFD93545BF61FF01473D11AC0F2B13C2@limkexm2.ad.analog.com> Content-Disposition: inline Sender: owner-linux-input@atrey.karlin.mff.cuni.cz List-Help: List-Owner: List-Post: List-Unsubscribe: To: "Hennerich, Michael" Cc: Bryan Wu , linux-input@atrey.karlin.mff.cuni.cz, linux-joystick@atrey.karlin.mff.cuni.cz, linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org, akpm@linux-foundation.org List-Id: linux-input@vger.kernel.org Hi Michael, On 10/15/07, Hennerich, Michael wrote: > > > >> + > >> +static int ad7877_read(struct device *dev, u16 reg) > >> +{ > >> + struct spi_device *spi = to_spi_device(dev); > >> + struct ser_req *req = kzalloc(sizeof *req, > GFP_KERNEL); > > > >How many reads can happen at once? Maybe allocate 1 ser_req per > >touchcsreen when creating it? > > ad7877_read_adc, ad7877_read and ad7877_write are just used by the sysfs > hooks. Touchscreen samples are read by the kthread using a different > message struct. So far each sysfs invocation got its own storage for the > spi message, which then is handed over to the SPI bus driver. > The SPI bus driver serializes transfers in a kthread. > > Two different processes could access the drivers sysfs hooks. > > Using one ser_req per touch screen could require additional locking? > Things at is, looks pretty safe to me. > OK, fair enough. -- Dmitry