On 11/28/2017 2:09 PM, Thomas Monjalon wrote:
> The pointer to the user parameter of the callback registration is
> automatically pass to the callback function.
> There is no point to allow changing this user parameter by a caller.
> That's why this parameter is always set to NULL by PMDs and set only
> in ethdev layer before calling the callback function.
It can be helpful to mention a little from history:
user cb_arg overwrite introduced by [1], to enable driver pass a pointer to user
callback function and carry some information back from app to driver.
Later to prevent usage of cb_arg as both input and output, an explicit output
(ret_param) added [2] to _rte_eth_dev_callback_process() but previous cb_arg
overwriting kept without any user.
[1]: c1ceaf3ad056 ("ethdev: add an argument to internal callback function")
[2]: d6af1a13d7a1 ("ethdev: add return values to callback process API")
>
> The NULL parameter in the internal callback processing function
> is now removed. It makes clear that the callback parameter is user
> managed and opaque from a DPDK point of view.
>
> Signed-off-by: Thomas Monjalon <tho...@monjalon.net>
Reviewed-by: Ferruh Yigit <ferruh.yi...@intel.com>
