查看“SPDIFRX Linux driver”的源代码

== Article purpose ==
本文介绍了适用于[[SPDIFRX internal peripheral]]的SPDIFRX  Linux<sup>&reg;</sup>驱动程序。

== Short Description ==
SPDIFRX<ref name="SPDIFRX internal peripheral">[[SPDIFRX internal peripheral]]</ref> Linux 驱动程序是在Linux[[ALSA_overview|ALSA framework]]中实现的ASoC CPU DAI驱动程序。

== Configuration ==

=== Kernel Configuration ===
Activate the SPDIFRX<ref name="SPDIFRX internal peripheral"/> Linux driver in the kernel configuration using the Linux Menuconfig tool: [[Menuconfig or how to configure kernel]]
<pre>
[*] Device Drivers
    [*] Sound card support
        [*] Advanced Linux Sound Architecture
            [*] ALSA for SoC audio support
                STMicroelectronics STM32 SOC audio support
	             [*] STM32 S/PDIF receiver (SPDIFRX) support
</pre>

=== Device tree ===
Refer to the [[SPDIFRX device tree configuration]] article when configuring the SPDIFRX Linux kernel driver.

== How to use ==
The SPDIFRX driver is accessed from userland through an ALSA device. Refer to [[ALSA_overview#How_to_use|ALSA overview]] to see how to list and use ALSA devices.

The SPDFIRX driver exposes an alsa control, which allows to retrieve the IEC958 status bits from
the input audio stream. 
{{Warning|The configuration of the SPDIFRX input pin in the device tree, may put some restrictions on the use of IEC958 control. Thus, in some configuration, the control can be used only when an audio stream is captured. Refer to the [[SPDIFRX device tree configuration]] article, to find details about SPDIFRX configuration.}}

== How to debug ==
The [[Debugfs|debugfs]] and procfs file systems can be checked to get information about the SPDFIRX driver and the resources it uses. A none exhaustive list of these file system entries is provided below. Refer to [[ALSA_overview#How_to_trace_and_debug_the_framework|ALSA overview]] to get more details about debugging tools.

* debugfs entries:
:* '''asoc''': refer to [[ALSA_overview#How_to_monitor]]
:* '''clk''': refer to [[Clock_overview#How_to_monitor_with_debugfs]] to get information on clocks.
:* '''pinctrl''': refer to [[Pinctrl_overview#How_to_monitor]] to get information on pins.
:* '''regmap''': allow to monitor SPDIFRX peripheral registers.
<div style="margin-left: 2em;">
 $ cat /sys/kernel/debug/regmap/xxx.audio-controller/registers
</div>
* procfs entries:
:* '''asound''': refer to [[ALSA_overview#How_to_debug]]
:* '''interrupts''': allow to check interrupts.
<div style="margin-left: 2em;">
 $ cat /proc/interrupts
</div>

== Source code location ==
{{CodeSource | Linux kernel | sound/soc/stm/stm32_spdifrx.c}}: implements the SPDIFRX driver.

==References==
<references />