[PATCH v5] wwan: core: Support slicing in port TX flow of WWAN subsystem

[Loic Poulain]

On Thu, 24 Nov 2022 at 08:47, <haozhe.chang at mediatek.com> wrote:
>
> From: haozhe chang <haozhe.chang at mediatek.com>
>
> wwan_port_fops_write inputs the SKB parameter to the TX callback of
> the WWAN device driver. However, the WWAN device (e.g., t7xx) may
> have an MTU less than the size of SKB, causing the TX buffer to be
> sliced and copied once more in the WWAN device driver.
>
> This patch implements the slicing in the WWAN subsystem and gives
> the WWAN devices driver the option to slice(by frag_len) or not. By
> doing so, the additional memory copy is reduced.
>
> Meanwhile, this patch gives WWAN devices driver the option to reserve
> headroom in fragments for the device-specific metadata.
>
> Signed-off-by: haozhe chang <haozhe.chang at mediatek.com>

Reviewed-by: Loic Poulain <loic.poulain at linaro.org>