From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757189AbZA1X2e (ORCPT ); Wed, 28 Jan 2009 18:28:34 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753142AbZA1X16 (ORCPT ); Wed, 28 Jan 2009 18:27:58 -0500 Received: from kroah.org ([198.145.64.141]:56970 "EHLO coco.kroah.org" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751931AbZA1X15 (ORCPT ); Wed, 28 Jan 2009 18:27:57 -0500 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: "Hans J. Koch" , Greg Kroah-Hartman Subject: [PATCH 2/3] UIO: Add missing documentation of features added recently Date: Wed, 28 Jan 2009 15:26:35 -0800 Message-Id: <1233185196-23064-2-git-send-email-gregkh@suse.de> X-Mailer: git-send-email 1.6.1 In-Reply-To: <20090128232543.GA23030@kroah.com> References: <20090128232543.GA23030@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Hans J. Koch The following features were added to the UIO framework in the near past: * Generic drivers for platform devices (uio_pdrv, uio_pdrv_genirq) * an "offset" sysfs attribute for memory mappings Unfortunately, all this went in without documentation (won't happen again...) This patch updates UIO documentation. Signed-off-by: Hans J. Koch Acked-by: Uwe Kleine-König Signed-off-by: Greg Kroah-Hartman --- Documentation/DocBook/uio-howto.tmpl | 88 ++++++++++++++++++++++++++++++++++ 1 files changed, 88 insertions(+), 0 deletions(-) diff --git a/Documentation/DocBook/uio-howto.tmpl b/Documentation/DocBook/uio-howto.tmpl index b787e47..52e1b79 100644 --- a/Documentation/DocBook/uio-howto.tmpl +++ b/Documentation/DocBook/uio-howto.tmpl @@ -42,6 +42,12 @@ GPL version 2. + 0.7 + 2008-12-23 + hjk + Added generic platform drivers and offset attribute. + + 0.6 2008-12-05 hjk @@ -312,6 +318,16 @@ interested in translating it, please email me pointed to by addr. + + + offset: The offset, in bytes, that has to be + added to the pointer returned by mmap() to get + to the actual device memory. This is important if the device's memory + is not page aligned. Remember that pointers returned by + mmap() are always page aligned, so it is good + style to always add this offset. + + @@ -594,6 +610,78 @@ framework to set up sysfs files for this region. Simply leave it alone. + +Using uio_pdrv for platform devices + + In many cases, UIO drivers for platform devices can be handled in a + generic way. In the same place where you define your + struct platform_device, you simply also implement + your interrupt handler and fill your + struct uio_info. A pointer to this + struct uio_info is then used as + platform_data for your platform device. + + + You also need to set up an array of struct resource + containing addresses and sizes of your memory mappings. This + information is passed to the driver using the + .resource and .num_resources + elements of struct platform_device. + + + You now have to set the .name element of + struct platform_device to + "uio_pdrv" to use the generic UIO platform device + driver. This driver will fill the mem[] array + according to the resources given, and register the device. + + + The advantage of this approach is that you only have to edit a file + you need to edit anyway. You do not have to create an extra driver. + + + + +Using uio_pdrv_genirq for platform devices + + Especially in embedded devices, you frequently find chips where the + irq pin is tied to its own dedicated interrupt line. In such cases, + where you can be really sure the interrupt is not shared, we can take + the concept of uio_pdrv one step further and use a + generic interrupt handler. That's what + uio_pdrv_genirq does. + + + The setup for this driver is the same as described above for + uio_pdrv, except that you do not implement an + interrupt handler. The .handler element of + struct uio_info must remain + NULL. The .irq_flags element + must not contain IRQF_SHARED. + + + You will set the .name element of + struct platform_device to + "uio_pdrv_genirq" to use this driver. + + + The generic interrupt handler of uio_pdrv_genirq + will simply disable the interrupt line using + disable_irq_nosync(). After doing its work, + userspace can reenable the interrupt by writing 0x00000001 to the UIO + device file. The driver already implements an + irq_control() to make this possible, you must not + implement your own. + + + Using uio_pdrv_genirq not only saves a few lines of + interrupt handler code. You also do not need to know anything about + the chip's internal registers to create the kernel part of the driver. + All you need to know is the irq number of the pin the chip is + connected to. + + + -- 1.6.0.2