> The driver certainly shouldn't offer VIRTIO_CONSOLE_F_DMA_MEM if you
> don't have DMA!
OK, so the feature table could be done like this:
static unsigned int features[] = {
VIRTIO_CONSOLE_F_SIZE,
VIRTIO_CONSOLE_F_MULTIPORT,
#if VIRTIO_CONSOLE_HAS_DMA
VIRTIO_CONSOLE_F_DMA_MEM,
#endif
}
If the device then asks for VIRTIO_CONSOLE_F_DMA_MEM
when DMA is not supported, virtio will do BUG_ON() from
virtio_check_driver_offered_feature().
Is this acceptable or should we add a check in virtcons_probe()
and let the probing fail instead?
E.g:
/* Refuse to bind if F_DMA_MEM request cannot be met */
if (!VIRTIO_CONSOLE_HAS_DMA &&
(vdev->config->get_features(vdev) & (1 << VIRTIO_CONSOLE_F_DMA_MEM))){
dev_err(&vdev->dev,
"DMA_MEM requested, but arch does not support DMA\n");
err = -EINVAL;
goto fail;
}
Regards,
Sjur
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