/proc/iomem 的内容 [英] Content of /proc/iomem
问题描述
1) 是否可以访问/proc/iomem 中未定义的物理地址?
1) Is it possible to access a physical address which is not defined in /proc/iomem?
2) 如果/proc/iomem 中没有出现设备的物理地址范围，是否表示该设备还没有被使用/初始化?
2) If the physical address range of a device does not appear in /proc/iomem, does it mean that the device has not been utilized/initialized yet?
推荐答案
1) 是否可以访问/proc/iomem 中未定义的物理地址?
1) Is it possible to access a physical address which is not defined in /proc/iomem?
是的.
假设内存映射所有直接连接的外围设备的 ARM 处理器，驱动程序可以执行 ioremap() 操作将物理内存映射到虚拟内存以供访问.
但是正确编写的驱动程序会首先调用 request_mem_region() 以确保它可以使用(并声称拥有)该物理地址空间./proc/iomem 中的信息来自调用 request_mem_region() 的驱动程序.
Yes.
Assuming an ARM processor which memory maps all directly-connected periperals, the driver could perform an ioremap() operation to map the physical memory to virtual memory for access.
But a properly written driver would first call request_mem_region() to ensure that it can use (and lay claim to) that physical address space.
The information in /proc/iomem comes from drivers calling request_mem_region().
2) 如果一个设备的物理地址范围没有出现在/proc/iomem 中，是否表示该设备还没有被使用/初始化?
2) If the physical address range of a device does not appear in /proc/iomem, does it mean that the device has not been utilized/initialized yet?
您必须检查驱动程序代码以确定驱动程序的编写情况.ioremap() 之前是否有 request_mem_region() ?
使用 dmesg 命令检查系统日志；可能驱动初始化失败.
You would have to inspect the driver code to determine how well written the driver is.
Is there a request_mem_region() before the ioremap()?
Check the system log using the dmesg command; perhaps driver initialization failed.
假设这是一个静态链接的驱动程序而不是一个可加载的模块，那么由于每个内核设备驱动程序都调用了它的 init() 例程，您可以通过添加选项initcall_debug"来获得跟踪输出" 在内核命令行上.如果您使用的是 U-Boot，则应将此选项添加到bootargs"变量(用于内核命令行).
Assuming that this is a statically-linked driver rather than a loadable module, then as each kernel device driver has its init() routine called you can get trace output by having added the option "initcall_debug" on the kernel command line. If you are using U-Boot, then this option should be added to the "bootargs" variable (which is used for the kernel command line).
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