virtqueue_add_outbuf(9)

💅 virtqueue_add_outbuf(9) — kernel API manual, bestie edition ✨

🌸 NAME 🌸

virtqueue_add_outbuf — expose output buffers to other end, and honestly? iconic.

✨ SYNOPSIS ✨

int virtqueue_add_outbuf (struct virtqueue *vq , struct scatterlist *sg
, unsigned int num , void *data , gfp_t gfp );

🎀 ARGUMENTS 🎀

• vq — the struct virtqueue we're talking about, periodt.
• sg — scatterlist (must be well-formed and terminated!), no cap.
• num — the number of entries in sg readable by other side.
• data — the token identifying the buffer.
• gfp — how to do memory allocations (if necessary).

💖 DESCRIPTION 💖

okay so bestie, here's the tea: the caller must ensure we don't call this with other virtqueue operations at the same time (except where noted, iykyk). That's the vibe check.

⚠️ no cap, this is important: don't run this concurrently with other virtqueue ops unless the docs say it's fine.

It returns zero or a negative error (ie. ENOSPC, ENOMEM, EIO). So if you get a negative number, it's giving "no space", "no memory", or "I/O error" energy. 💀

🦋 SEE ALSO 🦋

bestie, peep the kernel file ./drivers/virtio/virtio_ring.c and then these iconic functions:

• virtqueue_add_sgs(9)
• virtqueue_add_outbuf_premapped(9)
• virtqueue_add_inbuf(9)
• virtqueue_add_inbuf_cache_clean(9)
• virtqueue_add_inbuf_ctx(9)
• virtqueue_add_inbuf_premapped(9)
• virtqueue_dma_dev(9)
• virtqueue_kick_prepare(9)
• virtqueue_notify(9)
• virtqueue_kick(9)
• virtqueue_get_buf_ctx(9)
• virtqueue_disable_cb(9)
• virtqueue_enable_cb_prepare(9)
• virtqueue_poll(9)
• virtqueue_enable_cb(9)
• virtqueue_enable_cb_delayed(9)
• virtqueue_detach_unused_buf(9)
• vring_interrupt(9)
• virtqueue_resize(9)
• virtqueue_reset(9)
• virtqueue_get_vring_size(9)
• virtqueue_map_alloc_coherent(9)
• virtqueue_map_free_coherent(9)
• virtqueue_map_page_attrs(9)
• virtqueue_unmap_page_attrs(9)
• virtqueue_map_single_attrs(9)
• virtqueue_unmap_single_attrs(9)
• virtqueue_map_mapping_error(9)
• virtqueue_map_need_sync(9)
• virtqueue_map_sync_single_range_for_cpu(9)
• virtqueue_map_sync_single_range_for_device(9)

signing off from ./drivers/virtio — October 2026, virtqueue_add_outbuf(9) out! 💖✨🫶