Some Kindle screen refresh experiments...

[NiLuJe]

Related to #550

[NiLuJe]

Well, #550 in koreader/koreader, that is ;p. And PR #704 over there, too.

[houqp]

according to:

/*
 * Are we using FB or an alternate (overlay)
 * buffer for source of update?
 */
if (upd_data->flags & EPDC_FLAG_USE_ALT_BUFFER) {
    src_width = upd_data->alt_buffer_data.width;
    src_height = upd_data->alt_buffer_data.height;
    src_upd_region = &upd_data->alt_buffer_data.alt_update_region;
} else {
    src_width = fb_data->epdc_fb_var.xres_virtual;
    src_height = fb_data->epdc_fb_var.yres;
    src_upd_region = &upd_data->update_region;
}

and

if (upd_data->flags & EPDC_FLAG_USE_ALT_BUFFER) {
    sg_dma_address(&fb_data->sg[0]) =
        upd_data->alt_buffer_data.phys_addr + pxp_input_offs;
} else {
    sg_dma_address(&fb_data->sg[0]) =
        fb_data->info.fix.smem_start + fb_data->fb_offset + pxp_input_offs;
    sg_set_page(&fb_data->sg[0],
                virt_to_page(fb_data->info.screen_base),
                fb_data->info.fix.smem_len,
                offset_in_page(fb_data->info.screen_base));
}

Yes.

[NiLuJe]

@houqp : Hah, thanks :). From a practical standpoint, what would that be used for? Cheaply compositing something on top of the current fb?

[houqp]

I guess yes :P