Dear All,
I have gone through the file_storage gadget driver code which exists
in the drivers/usb/gadget folder. I understood the code flow a bit.
However, I did not understand about the following variable.
fsg->next_buffhd_to_fill
The above variable is defined in the main device structure, struct
fsg_dev. As explained in the comments "There is a variable
(fsg->next_buffhd_to_fill) that points to the next buffer head to
use".
As explained in the comments, that was used directly from the fsg main
structure in all the functions like get_next_command, do_read,
do_write, do_verify etc. In all these functions the following
statement was used.
bh = fsg->next_buffhd_to_fill;
where bh is a struct fsg_buffhd structure type.
My doubt about this variable is, how it will be filled and where it
will be filled? I have used the dummy hcd driver for this.
I have also seen that there is a wake up call to the sleeping thread
from all the completion callback routines like bulk_out_complete,
bulk_in_complete. There is a statement like
struct fsg_buffhd *bh = req->context;
How can the req->context is equivalent to the struct fsg_buffhd? OR Is
there any API that passes the struct fsg_buffhd pointer to the upper
layers like dummy hcd / usb core?
Sorry, If I have asked very silly questions. Any help would be greatly
appreciated and helps a lot to me.
Thanks in advance.
With Regards,
Madhavi M.
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