On Fri, Jul 26, 2024 at 04:15:03PM +0100, Jonathan Cameron wrote:

On Mon, 24 Jun 2024 19:47:27 -0300
Jason Gunthorpe [off-list ref] wrote:

quoted

Userspace will need to know some details about the fwctl interface being
used to locate the correct userspace code to communicate with the
kernel. Provide a simple device_type enum indicating what the kernel
driver is.

As below - maybe consider a UUID?
Would let you decouple allocating those with upstreaming drivers.
We'll just get annoying races on the enum otherwise as multiple
drivers get upstreamed that use this.

I view the coupling as a feature - controlling uABI number assignment
is one of the subtle motivations the kernel community has typically
used to encourage upstream participation.

quoted

 static dev_t fwctl_dev;
 static DEFINE_IDA(fwctl_ida);
 
+DEFINE_FREE(kfree_errptr, void *, if (!IS_ERR_OR_NULL(_T)) kfree(_T));

Why need for a new one?  That's the same as the one in slab.h from
6.9 onwards. Before that it was
if (_T)

I was going to suggest promoting this to slab.h and then found
the normal implementation had been improved since I last checked.

Same, now it is improved it can go away.

quoted

+/**
+ * struct fwctl_info - ioctl(FWCTL_INFO)
+ * @size: sizeof(struct fwctl_info)
+ * @flags: Must be 0
+ * @out_device_type: Returns the type of the device from enum fwctl_device_type

Maybe a UUID?  Avoid need to synchronize that list for ever.

quoted

+ * @device_data_len: On input the length of the out_device_data memory. On
+ *	output the size of the kernel's device_data which may be larger or
+ *	smaller than the input. Maybe 0 on input.
+ * @out_device_data: Pointer to a memory of device_data_len bytes. Kernel will
+ *	fill the entire memory, zeroing as required.

Why do we need device in names of these two?

I'm not sure I understand this question?

out_device_type returns the "name"

out_device_data returns a struct of data, the layout of the struct is
defined by out_device_type

Jason