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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Simon Horman , tariqt@nvidia.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH net-next] net: devmem: add netdev_has_dmabuf_binding() helper Message-ID: References: <20260810175446.3945358-2-dtatulea@nvidia.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20260810175446.3945358-2-dtatulea@nvidia.com> On 08/10, Dragos Tatulea wrote: > Currently there is no way to check if there is a dmabuf bound on a TX > queue. RX side has netif_rxq_has_unreadable_mp() which gives a hint of > it. > > To help with that, this patch add a helper to check whether a devmem > dmabuf binding is active on a given netdev, optionally filtered by the > DMA device the dmabuf was mapped against. > > This API is necessary for the upcoming support of data direct in mlx5e > to allow blocking accidental swapping of DMA devices while devmem is active. > > Signed-off-by: Dragos Tatulea > --- > include/net/netmem.h | 19 +++++++++++++++++++ > net/core/devmem.c | 20 ++++++++++++++++++++ > 2 files changed, 39 insertions(+) > > diff --git a/include/net/netmem.h b/include/net/netmem.h > index bccacd21b6c3..0e332e04ea16 100644 > --- a/include/net/netmem.h > +++ b/include/net/netmem.h > @@ -363,16 +363,35 @@ static inline unsigned long netmem_get_dma_addr(netmem_ref netmem) > return netmem_to_nmdesc(netmem)->dma_addr; > } > > +struct net_device; > + > #if defined(CONFIG_NET_DEVMEM) > static inline bool net_is_devmem_iov(const struct net_iov *niov) > { > return niov->type == NET_IOV_DMABUF; > } > + > +/** > + * netdev_has_dmabuf_binding - is there a dmabuf binding for a > + * given @dev and @dma_dev > + * > + * @dev: netdev to check bindings > + * @dma_dev: dma device to check, when NULL it will not be checked > + * > + * Return: true if a binding is found under @dev and possibily @dma_dev > + */ > +bool netdev_has_dmabuf_binding(struct net_device *dev, struct device *dma_dev); > #else > static inline bool net_is_devmem_iov(const struct net_iov *niov) > { > return false; > } > + > +static inline bool netdev_has_dmabuf_binding(struct net_device *dev, > + struct device *dma_dev) > +{ > + return false; > +} > #endif > > void __get_netmem(netmem_ref netmem); > diff --git a/net/core/devmem.c b/net/core/devmem.c > index 957d6b96216b..f13a0e343684 100644 > --- a/net/core/devmem.c > +++ b/net/core/devmem.c > @@ -364,6 +364,26 @@ struct net_devmem_dmabuf_binding *net_devmem_lookup_dmabuf(u32 id) > return binding; > } > > +bool netdev_has_dmabuf_binding(struct net_device *dev, struct device *dma_dev) > +{ > + struct net_devmem_dmabuf_binding *binding; > + unsigned long id; > + bool found = false; xmas tree. Other than that LGTM. Presumably it's better to ship via your upcoming series to show the actual usage?