Implementation of linux char driver with multiple parameters to access

Question

I am writing a simple char driver which accesses a PCI card. It is registered to sysfs with the help of a new class and accessible under /dev/foodev . Using standard file operations I can perform simple read and write operations to the device.

My problem: I have multiple parameters stored at different addresses on the card (version, status, control, ...) which I would like access independently. Currently having only one read and one write function I therefore have to change the address every time again in the driver code. Obviously there is a more convenient way to implement this. I stumbled about the two following approaches and was wondering which is the better one in terms of sustainability and user accessibility:

• Using ioctl commands setting the address/parameter before an access.

• Having the device already nicely set up in udev using multiple attributes ( device_create_file() ) of which the user than just can write/read from different "files":

  /dev/foodev ../version ../status ../control

Answer 1

我认为您应该看一下PCI框架来实现驱动程序。

Answer 2

Don't (mis)use ioctls; you'll have race conditions. Use the attributes as files. That scheme is already used in sysfs. EG look at GPIO LEDs and keys. – sawdust