From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756622AbdESTLR (ORCPT ); Fri, 19 May 2017 15:11:17 -0400 Received: from mail.kernel.org ([198.145.29.99]:53658 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756574AbdESTKr (ORCPT ); Fri, 19 May 2017 15:10:47 -0400 DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5B4C8239DD Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=mcgrof@kernel.org From: "Luis R. Rodriguez" To: gregkh@linuxfoundation.org Cc: wagi@monom.org, dwmw2@infradead.org, rafal@milecki.pl, arend.vanspriel@broadcom.com, rjw@rjwysocki.net, yi1.li@linux.intel.com, atull@opensource.altera.com, moritz.fischer@ettus.com, pmladek@suse.com, johannes.berg@intel.com, emmanuel.grumbach@intel.com, luciano.coelho@intel.com, kvalo@codeaurora.org, luto@kernel.org, torvalds@linux-foundation.org, keescook@chromium.org, takahiro.akashi@linaro.org, dhowells@redhat.com, pjones@redhat.com, hdegoede@redhat.com, alan@linux.intel.com, tytso@mit.edu, linux-kernel@vger.kernel.org, "Luis R. Rodriguez" Subject: [PATCH v8 4/5] firmware: document the extensible driver data API Date: Fri, 19 May 2017 12:10:39 -0700 Message-Id: <20170519191040.25165-5-mcgrof@kernel.org> X-Mailer: git-send-email 2.11.0 In-Reply-To: <20170519191040.25165-1-mcgrof@kernel.org> References: <20170502084914.23588-1-mcgrof@kernel.org> <20170519191040.25165-1-mcgrof@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This documents the driver data API. Signed-off-by: Luis R. Rodriguez --- Documentation/driver-api/firmware/driver_data.rst | 167 +++++++++++++++++++++ Documentation/driver-api/firmware/index.rst | 1 + Documentation/driver-api/firmware/introduction.rst | 16 ++ .../driver-api/firmware/request_firmware.rst | 2 + 4 files changed, 186 insertions(+) create mode 100644 Documentation/driver-api/firmware/driver_data.rst diff --git a/Documentation/driver-api/firmware/driver_data.rst b/Documentation/driver-api/firmware/driver_data.rst new file mode 100644 index 000000000000..be7c7ff99151 --- /dev/null +++ b/Documentation/driver-api/firmware/driver_data.rst @@ -0,0 +1,167 @@ +.. _driver_data: + +=============== +driver_data API +=============== + +The driver data APIs provides a flexible API for general driver data file +lookups. Its flexibility aims at mitigating collateral evolutions on the kernel +as new functionality is introduced. + +Driver data modes of operation +============================== + +There are two types of modes of operation for driver data requests: + + * synchronous - driver_data_request_sync() + * asynchronous - driver_data_request_async() + +Synchronous requests expect requests to be done immediately, asynchronous +requests enable requests to be scheduled for a later time. + +Driver data request parameters +============================== + +Variations of types of driver data requests are specified by a driver data +request parameter data structure. The flexibility of the API is provided by +expanding the request parameters as new functionality is needed, without +loosely modifying or adding new exported APIs. + +driver_data_sync_cbs +-------------------- +.. kernel-doc:: include/linux/driver_data.h + :functions: driver_data_sync_cbs + +driver_data_async_cbs +--------------------- +.. kernel-doc:: include/linux/driver_data.h + :functions: driver_data_async_cbs + +driver_data_cbs +--------------- +.. kernel-doc:: include/linux/driver_data.h + :functions: driver_data_cbs + +driver_data_reqs +---------------- +.. kernel-doc:: include/linux/driver_data.h + :functions: driver_data_reqs + +driver_data_req_params +---------------------- +.. kernel-doc:: include/linux/driver_data.h + :functions: driver_data_req_params + +Synchronous driver data requests +================================ + +Synchronous driver data requests will wait until the driver data is found or +until an error is returned. + +driver_data_request_sync +------------------------ +.. kernel-doc:: drivers/base/firmware_class.c + :functions: driver_data_request_sync + +Asynchronous driver data requests +================================= + +Asynchronous driver data requests allow driver code to not have to wait +until the driver data or an error is returned. Function callbacks are +required so that when the firmware or an error is found the driver is +informed through the callbacks. Asynchronous driver data requests cannot +be called from atomic contexts. + +driver_data_request_async +------------------------- +.. kernel-doc:: drivers/base/firmware_class.c + :functions: driver_data_request_async + +Reference counting and releasing the driver data file +===================================================== + +The device and module are bumped with reference counts during the driver data +requests. This prevents removal of the device and module making the driver data +request call until the driver data request callbacks have completed, either +synchronously or asynchronously. When synchronous requests are made the +firmware_class is refcounted. When asynchronous requests are made the caller's +module is refcounted. Asynchronous requests do not refcount the firmware_class +module. + +The driver data request API enables callers to provide a callback for both +synchronous and asynchronous requests and since consumption can be expected +in these callbacks it frees it for you by default after callback handlers +are issued. If you wish to keep the driver data around after your callbacks +you must specify this through the driver data request parameter data structure. + +Driver data private internal functionality +========================================== + +This section documents functionality not exposed to users, but important in +understanding how the driver data internals work. + +driver_data_mode +---------------- +.. kernel-doc:: drivers/base/firmware_class.c + :functions: driver_data_mode + +driver_data_priv_reqs +--------------------- +.. kernel-doc:: drivers/base/firmware_class.c + :functions: driver_data_priv_reqs + +driver_data_priv_params +----------------------- +.. kernel-doc:: drivers/base/firmware_class.c + :functions: driver_data_priv_params + +driver_data_params +------------------ +.. kernel-doc:: drivers/base/firmware_class.c + :functions: driver_data_params + +Testing the driver_data API +=========================== + +The driver data API has a selftest driver: lib/test_driver_data.c. The +test_driver_data enables you to build your tests in userspace by exposing knobs +of the exported API in userspace and enabling userspace to configure and +trigger a kernel call. This lets us build most possible test cases of +the kernel APIs from userspace. + +The test_driver_data also enables multiple test triggers to be created +enabling testing to be done in parallel, one test interface per test case. + +To test an async call one could do:: + + echo anything > /lib/firmware/test-driver_data.bin + echo -n 1 > /sys/devices/virtual/misc/test_driver_data0/config_async + echo -n 1 > /sys/devices/virtual/misc/test_driver_data0/trigger_config + +A series of tests have been written to test the driver data API thoroughly. +A respective test case is expected to bet written as new features get added. +For details of existing tests run:: + + tools/testing/selftests/firmware/driver_data.sh -l + +To see all available options:: + + tools/testing/selftests/firmware/driver_data.sh --help + +To run a test 0010 case 40 times:: + + tools/testing/selftests/firmware/driver_data.sh -c 0010 40 + +Note that driver_data.sh uses its own temporary custom path for creating and +looking for driver data files, it does this to not overwrite any production +files you might have which may share the same names used by the test shell +script driver_data.sh. If you are not using the driver_data.sh script your +default path will be used. + +Tracking development enhancements and ideas +=========================================== + +To help track ongoing development for firmware_class and related items to +firmware_class refer to the kernel newbies wiki page [0]. + +[0] http://kernelnewbies.org/KernelProjects/firmware-class-enhancements diff --git a/Documentation/driver-api/firmware/index.rst b/Documentation/driver-api/firmware/index.rst index 29da39ec4b8a..70a3dea0c5de 100644 --- a/Documentation/driver-api/firmware/index.rst +++ b/Documentation/driver-api/firmware/index.rst @@ -8,6 +8,7 @@ Linux Firmware API core request_firmware other_interfaces + driver_data .. only:: subproject and html diff --git a/Documentation/driver-api/firmware/introduction.rst b/Documentation/driver-api/firmware/introduction.rst index 211cb44eb972..c1173bac0dbb 100644 --- a/Documentation/driver-api/firmware/introduction.rst +++ b/Documentation/driver-api/firmware/introduction.rst @@ -25,3 +25,19 @@ are already using asynchronous initialization mechanisms which will not stall or delay boot. Even if loading firmware does not take a lot of time processing firmware might, and this can still delay boot or initialization, as such mechanisms such as asynchronous probe can help supplement drivers. + +Two APIs +======== + +Two APIs are provided for firmware: + +* Old firmware API - :ref:`request_firmware` +* Flexible driver data API - :ref:`driver_data` + +We have historically extended the firmware API by adding new routines or at +times extending existing routines with more or less arguments. This doesn't +scale well, when new arguments are added to existing routines it means we need +to traverse the kernel with a slew of collateral evolutions to adjust old +driver users. The driver data API is an extensible API enabling extensions to +be added by avoiding unnecessary collateral evolutions as features get added. +New features and development should be added through the driver_data API. diff --git a/Documentation/driver-api/firmware/request_firmware.rst b/Documentation/driver-api/firmware/request_firmware.rst index 1c2c4967cd43..b31938244b7f 100644 --- a/Documentation/driver-api/firmware/request_firmware.rst +++ b/Documentation/driver-api/firmware/request_firmware.rst @@ -1,3 +1,5 @@ +.. _request_firmware: + ==================== request_firmware API ==================== -- 2.11.0