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From: David Brownell <david-b@pacbell.net>
To: benh@kernel.crashing.org, avorontsov@ru.mvista.com
Cc: linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org,
	i2c@lm-sensors.org, Jean Delvare <khali@linux-fr.org>,
	David Miller <davem@davemloft.net>
Subject: Re: [PATCH 4/7] gpiolib: implement dev_gpiochip_{add,remove} calls
Date: Tue, 21 Oct 2008 21:22:48 -0700	[thread overview]
Message-ID: <200810212122.49121.david-b@pacbell.net> (raw)
In-Reply-To: <1224642497.7654.319.camel@pasglop>

On Tuesday 21 October 2008, Benjamin Herrenschmidt wrote:
> The notifier can be registered before the devices, though it's a little
> bit fishy and fragile.
> 
> Easier I suppose to just have OF specific hooks in the bus code.

Like what I suggested:  "chip-aware OF glue drivers".  The relevant
bus code being the "of_platform_bus_type" infrastructure.

Example:  instead of Anton's patch #6 modifying the existing pca953x
driver, an of_pca953x driver that knows how to poke around in the OF
device attributes to (a) create the pca953x_platform_data, (b) call
i2c_register_board_info() to make that available later, and then
finally (c) vanish, since it's not needed any longer.

Better that than either the $SUBJECT patch, or modifying gpiolib to
grow OF-specific hooks ... hooks that can at best solve *one* of the
problems:  which GPIO numbers to use with this chip.  The platform
data does solve other problems(*) like:  (i) how to initialize the
polarity inversion register, (ii) arranging to set up other devices
only after their GPIOs are ready, (iii) initializing things that
device drivers won't always know about, or which may need to be
set up before such drivers are available.

- Dave

(*) A trivial example of (ii) would be LEDs driven by those GPIOs.

    A less trivial example:  see arch/arm/mach-davinci/board-evm.c
    in current GIT.  There are three pcf8574 I2C expanders used for
    various things ... LEDs, audio PLL, device power supplies, reset
    lines for external devices, more.

  parent reply	other threads:[~2008-10-22  4:23 UTC|newest]

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-10-16 17:12 [PATCH 0/7 RFC] Handle I2C GPIO controllers with the OF (was: pca9539 I2C gpio expander) Anton Vorontsov
2008-10-16 17:12 ` [PATCH 1/7] powerpc and sparc: introduce dev_archdata node accessors Anton Vorontsov
2008-10-16 22:36   ` David Miller
2008-10-16 23:02     ` Grant Likely
2008-10-16 17:12 ` [PATCH 2/7] i2c: add info->archdata field Anton Vorontsov
2008-10-17  9:21   ` Jean Delvare
2008-10-22  0:27     ` Benjamin Herrenschmidt
2008-10-22  6:50       ` Jean Delvare
2008-10-22  7:37         ` Benjamin Herrenschmidt
2008-10-22 10:08           ` Anton Vorontsov
2008-10-22 11:07             ` Jean Delvare
2008-10-22 12:50               ` Anton Vorontsov
2008-10-16 17:12 ` [PATCH 3/7] of: fill the archdata for I2C devices Anton Vorontsov
2008-10-22  4:14   ` Grant Likely
2008-10-16 17:12 ` [PATCH 4/7] gpiolib: implement dev_gpiochip_{add,remove} calls Anton Vorontsov
2008-10-17 20:24   ` David Brownell
2008-10-17 21:29     ` Anton Vorontsov
2008-10-20  7:29       ` David Brownell
2008-10-20 15:48         ` Anton Vorontsov
2008-10-22  0:29           ` Benjamin Herrenschmidt
2008-10-22  1:03             ` Anton Vorontsov
2008-10-22  1:42               ` Anton Vorontsov
2008-10-22  2:28                 ` Benjamin Herrenschmidt
2008-10-22  4:20                   ` Grant Likely
2008-10-22  4:22                   ` David Brownell [this message]
2008-10-22 10:36                     ` Anton Vorontsov
2008-10-22 10:46                       ` Anton Vorontsov
2008-10-22 18:32                         ` Anton Vorontsov
2008-10-22 21:04                           ` David Brownell
2008-10-22 21:22                             ` Anton Vorontsov
2008-10-22 21:52                               ` David Brownell
2008-10-22 22:29                                 ` Anton Vorontsov
2008-10-23  5:19                                   ` David Brownell
2008-10-23  4:45                             ` Benjamin Herrenschmidt
2008-10-23  6:06                               ` David Brownell
2008-10-23  6:15                           ` David Brownell
2008-10-28 17:45                         ` [PATCH 0/6 RFC] OF-glue devices for I2C/SPI (was: " Anton Vorontsov
2008-10-28 17:46                           ` [PATCH 1/6] of/base: Add new helper of_should_create_pdev() Anton Vorontsov
2008-10-28 17:46                           ` [PATCH 2/6] of/of_i2c: implement of_{,un}register_i2c_device Anton Vorontsov
2008-10-28 17:46                           ` [PATCH 3/6] of/of_i2c: add support for dedicated OF I2C devices Anton Vorontsov
2008-10-28 18:41                             ` David Miller
2008-10-28 17:46                           ` [PATCH 4/6] of/gpio: add support for two-stage registration for the of_gpio_chips Anton Vorontsov
2008-10-28 17:46                           ` [PATCH 5/6] gpio/pca953x: pass gpio_chip pointer to the setup/teardown callbacks Anton Vorontsov
2008-10-28 17:46                           ` [PATCH 6/6] gpio: OpenFirmware bindings for the pca953x Anton Vorontsov
2008-10-28 17:53                           ` [PATCH 0/6 RFC] OF-glue devices for I2C/SPI (was: Re: [PATCH 4/7] gpiolib: implement dev_gpiochip_{add,remove} calls Grant Likely
2008-10-22  2:27               ` Benjamin Herrenschmidt
2008-10-16 17:13 ` [PATCH 5/7] of/gpio: implement of_dev_gpiochip_{add,remove} calls Anton Vorontsov
2008-10-17 20:25   ` David Brownell
2008-10-17 21:13     ` Anton Vorontsov
2008-10-16 17:13 ` [PATCH 6/7] gpio/pca953x: convert to dev_gpiochip_add and make it work with the OF Anton Vorontsov
2008-10-16 17:13 ` [PATCH 7/7] i2c/mcu_mpc8349emitx: convert to the new I2C/OF/GPIO infrastructure Anton Vorontsov
2008-10-17 16:07 ` [PATCH 0/7 RFC] Handle I2C GPIO controllers with the OF (was: pca9539 I2C gpio expander) Steven A. Falco

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