查看“DAC Linux driver”的源代码

== Article purpose ==
本文介绍了用于DAC  driver for the DAC<ref name="DAC internal peripheral">[[DAC internal peripheral]]</ref> 内部外围设备的Linux<sup>&reg;</sup>驱动程序：
* 驱动程序支持哪些DAC功能
* 如何配置，使用和调试驱动程序
* 驱动程序的结构是什么，以及在哪里可以找到源代码

== Short Description ==
DAC Linux<sup>&reg;</sup> 驱动程序（内核空间）基于 [[IIO overview|IIO]] 框架。
它实现了'''IIO直接模式'''，以在每个通道上独立执行单个转换。<br/>

== Configuration ==
=== Kernel configuration ===
使用Linux Menuconfig工具在内核配置中激活DAC <ref name="DAC internal peripheral"/> Linux<sup>&reg;</sup> 驱动程序： [[Menuconfig or how to configure kernel]] (启用CONFIG_STM32_DAC).
<pre>
Device Drivers  --->
   <*> Industrial I/O support  --->
      Digital to analog converters  --->
         <*> STMicroelectronics STM32 DAC
</pre>

=== Device tree ===
配置DAC Linux内核驱动程序时，请参考[[DAC device tree configuration]] 文章。

== How to use ==
在“ IIO直接模式”下，可以直接通过sysfs完成转换。 请参阅 [[How to use the IIO user space interface#How to do a simple DAC conversion using the sysfs interface|How to do a simple DAC conversion using the sysfs interface]]。

== How to trace and debug ==
有关如何在驱动程序和框架中启用调试日志的信息，请参考[[IIO_overview#How_to_trace_with_dynamic_debug|How to trace with dynamic debug]]。

有关如何访问DAC寄存器的信息，请参考[[IIO_overview#How_to_debug_with_debugfs|How to debug with debugfs]]。

DAC对其他关键资源具有系统范围的依赖性：
* 可以禁用'''运行时电源管理'''，例如，可以通过“ power / control” sysfs条目将其强制为'''on'''。
 {{Board$}} cd /sys/devices/platform/soc/40017000.dac/40017000.dac\:dac@1/
 {{Board$}} cat power/autosuspend_delay_ms
 2000
 {{Board$}} cat power/control
 auto                                     # kernel is allowed to automatically suspend the ADC device after autosuspend_delay_ms
 {{Board$}} {{highlight|echo on > power/control}}         # force the kernel to resume the DAC device (e.g. keep clocks and regulators enabled)
{{Info| 禁用运行时电源管理可能很有用，以便通过任何方式转储寄存器或检查时钟和调节器的使用情况（请参见下面的示例）。}}

* 可以通过阅读“ clk_summary”来验证'''clock'''<ref name="Clock overview">[[Clock overview]]</ref> 的使用情况：
 {{Board$}} {{highlight|cat /sys/kernel/debug/clk/clk_summary}} | grep dac
        dac12_k                        0        0        0       32000          0 0
                       dac12           1        2        0    98303955          0 0

* '''regulator'''<ref name="Regulator overview">[[Regulator overview]]</ref> 树和使用情况可以通过以下方式进行验证（例如，使用计数，开路计数和调节器参考电压）：
 {{Board$}} {{highlight|cat /sys/kernel/debug/regulator/regulator_summary}}
  regulator                      use open bypass voltage current     min     max
 -------------------------------------------------------------------------------
     v3v3                          4    5      0  3300mV     0mA  3300mV  3300mV
        vdda                       1    2      0  2900mV     0mA  2900mV  2900mV
           40017000.dac                                              0mV     0mV
           48003000.adc                                              0mV     0mV

* '''pinctrl'''<ref name="Pinctrl_overview">[[Pinctrl overview]]</ref> 的用法可以通过阅读“ pinmux-pins”来验证：
 {{Board$}} cd /sys/kernel/debug/pinctrl/soc\:pin-controller@50002000/
 {{Board$}} {{highlight|cat pinmux-pins}} | grep dac
 pin 4 (PA4): device 40017000.dac function {{highlight|analog}} group PA4
 pin 5 (PA5): device 40017000.dac function {{highlight|analog}} group PA5   # check pins are assigned to DAC and configured as "analog"

== Source code location ==
The DAC source code is composed of:
* {{CodeSource | Linux kernel | drivers/iio/dac/stm32-dac-core.c | stm32-dac-core driver}} to handle common resources  such as [[Clock overview|clock]] or [[Regulator overview|regulator]] used as reference voltage and common registers.
* {{CodeSource | Linux kernel | drivers/iio/dac/stm32-dac.c | stm32-dac driver}} to handle the resources available for each DAC such as channel configuration or output buffer handling (power-down mode).

==References==
<references />