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I want to create a binary file in /sys/class/mydev/bitmap to indicate the absence of my device. But it seems that there is no Linux kernel API (like create_device_bin_file) to create a binary file in the class directory. How can I get that?

I have already created a character attribute file in the mydev class. The code is as follows

static int __init module_init(void) { attr.show = pciex_devshow; attr.store = pciex_devstore; attr.attr.name = "state"; attr.attr.mode = S_IRUSR | S_IWUSR; class_create_file(pciex_class, &attr); } static ssize_t pciex_devshow(struct device *dev, struct device_attribute *attr, char *buf) { struct dev_private *pdev; return snprintf(buf, PAGE_SIZE, "%c\r\n", dev_bitmap); }

dev_bitmap is a hex format variable, how can I explore it to userspace?

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I believe what you're after are these functions:

  • class_create
  • class_destroy

etc. located in include/linux/device.h.

Here's (a bit outdated - function signatures changed a little since then) tutorial how to work with this interface.

drivers/s390/char/tape_class.c contains a good example of creating a device that communicates through this interface.

Also this answer looks like it's going to be helpful.

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I have created a char attribute file in /sys/class/mydev/status by calling class_create_file. The file status can expore kernel object in character, but I want it in hex or bin format. In other words, I want to create a binary format in a existing class. Does it possible?
What does prevent you from interpreting the input/output in the driver itself the way you need?

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