在什么条件下/ sys / kernel / debug / gpio为空？ [英] Under what conditions would /sys/kernel/debug/gpio be empty?

问题描述

摘要

我的目标是在英特尔主板（具有C1037U处理器的NM70芯片组）上控制Peppermint 4 Linux（内核版本3.8.0）中的GPIO引脚。

我正在调试我使用sysfs界面的问题，并试图了解/ sys / kernel / debug / gpio为空的条件？ p>

尝试通过

echo XX> / sys / class / gpio / export

对于XX从0到255，我收到以下错误消息

echo：write error：没有这样的设备

在什么条件下/ sys / kernel / debug / gpio为空？

背景

• 主板：Intel使用NM70芯片组


• 处理器：C1037U处理器


• 操作系统：Peppermint 4 Linux


• 内核版本：3.8。 0


• GPIO界面：sysfs

我试图使用sysfs界面，允许通过文件系统从用户空间访问GPIO引脚。

我已经成功地遵循了 https://help.ubuntu.com/community/Kernel/Compile 按顺序重新编译内核暴露用户空间中的GPIO访问并打开调试模式对于GPIO：

一旦新的内核被编译，我可以第一次看到/ sys / class / gpio中的GPIO文件夹。那么在理论上应该是能够通过写入文件系统来打开/关闭GPIO端口的情况。这种方法在 http：/ /falsinsoft.blogspot.co.uk/2012/11/access-gpio-from-linux-user-space.html 。

尝试导出时pin 0到255 by

echo XX> / sys / class / gpio / export

对于XX从0到255，我收到以下错误消息

echo：write error：没有这样的设备

尝试导出外部引脚范围0到255由

echo XX> / sys / class / gpio / export

我收到以下错误消息

echo：write error：无效的参数

本教程建议这可能是因为GPIO端口被保留给另一个程序，如果是这样，调试文件（/ sys / kernel / debug / gpio）将能够显示它们在哪里保留。

然而，/ sys / kernel / debug / gpio为空。

我可以看到并控制BIOS中的GPIO引脚（将引脚更改为输入或输出为高电平/低电平）。 >

相关问题

启用GPIO

解决方案

/ sys /如果没有注册的GPIO设备，kernel / debug / gpio将为空（警告：当我说GPIO设备，我不是指硬件，而是内核表示）。

所以，这些GPIO设备是在运行时由内核注册并与特定的GPIO设备驱动程序相关联。

依次选择GPIO设备驱动程序并将其关联到给定的设备，因为它是声明与GPIO设备的兼容性。

例如，内核将匹配PCI供应商和产品ID，并探测一个GPIO驱动程序支持该PCI供应商/产品。当GPIO驱动程序被探测时，它通常会注册GPIO设备实例。

最后，注册的GPIO设备是提供/ sys / kernel / debug / gpio中显示的GPIO 。

以上是Linux中所谓的设备驱动程序模型的一部分。虽然这有点过时了，但您可以阅读[1]。

现在，看看您需要为您的NM70芯片组选择GPIO驱动程序。维基百科说，芯片组代号是Panther Point-M[2]。有一些运气，lpc_ich驱动程序可以支持它。您必须使用CONFIG_LPC_ICH = y构建您的内核。

或者，如果您的GPIO由PCI设备提供，您可以使用 lspci 获取ID，然后在这些ID的内核源中grep。

[1] http://www.oreilly.com/openbook/linuxdrive3/book/ch14.pdf

[2] https://en.wikipedia.org/wiki/List_of_Intel_chipsets

Summary

My aim is to control the GPIO pins in Peppermint 4 Linux (Kernel version 3.8.0) on an Intel motherboard (NM70 chipset with C1037U processor).

I'm debugging issues I'm having using the sysfs interface and am trying to understand the conditions where /sys/kernel/debug/gpio would be empty?

When attempting to export pins 0 to 255 by

echo XX > /sys/class/gpio/export

for XX from 0 to 255, I get the following error message

echo: write error: No such device

Under what conditions would /sys/kernel/debug/gpio be empty?

 Background

• Motherboard: Intel with NM70 chipset
• Processor: C1037U processor
• OS: Peppermint 4 Linux
• Kernel version: 3.8.0
• GPIO interface: sysfs

I'm attempting to use the sysfs interface, which allows GPIO pins to be accessed from userspace through the filesystem.

I’ve successfully followed the "Alternate Build Method: The Old-Fashioned Debian Way" section of https://help.ubuntu.com/community/Kernel/Compile to recompile the kernel in order to expose GPIO access in user space and to turn on debug mode for GPIO:

Once the new kernel was compiled, I was able to see the GPIO folder in /sys/class/gpio for the first time. Then, in theory, it should be a case of being able to turn GPIO ports ON/OFF by writing to the filesystem. This approach is outlined at http://falsinsoft.blogspot.co.uk/2012/11/access-gpio-from-linux-user-space.html.

When attempting to export pins 0 to 255 by

echo XX > /sys/class/gpio/export

for XX from 0 to 255, I get the following error message

echo: write error: No such device

When attempting to export pins outside the range 0 to 255 by

echo XX > /sys/class/gpio/export

I get the following error message

echo: write error: Invalid argument

The tutorial suggests this could be because the GPIO ports are reserved for another program and that, if so, the debug file (/sys/kernel/debug/gpio) would be able to show where they are reserved.

However, /sys/kernel/debug/gpio is empty.

I can see and control the GPIO pins in the BIOS (change pins to be input or output HIGH/LOW).

Related questions

writing to /sys/class/gpio/export failing

Enable pullup GPIO

解决方案

/sys/kernel/debug/gpio will be empty if there no GPIO device registered (warning: when I say GPIO device, I don't mean the piece of hardware, but rather the kernel representation of it).

So, these GPIO devices are registered at runtime by the kernel and associated to a specific GPIO device driver.

In turn, the GPIO device driver is selected and associated to a given device, because it is the one declaring compatibility with said GPIO device.

E.g., the kernel would match on PCI vendor and product ID, and probe a GPIO driver that claims support for that PCI vendor/product. When the GPIO driver is probed, it typically registers the GPIO device instance.

Finally, that registered GPIO device is what provides GPIOs shown in /sys/kernel/debug/gpio.

The above is part of the so-called "Device Driver model" in Linux. Although it's a bit outdated, you can read [1].

Now, let's see what GPIO driver you need to select for your NM70 chipset. Wikipedia says that the chipset codename is "Panther Point-M" [2]. With some luck, the lpc_ich driver could support it. You would have to build your kernel with CONFIG_LPC_ICH=y.

Alternatively, if your GPIOs are provided by a PCI device, you could use lspci to get the IDs, and then grep in the kernel sources for those IDs.

[1] http://www.oreilly.com/openbook/linuxdrive3/book/ch14.pdf

[2] https://en.wikipedia.org/wiki/List_of_Intel_chipsets

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