Re: [dpdk-dev] [PATCH v8] dmadev: introduce DMA device library

[Jerin Jacob <jerinjacobk@gmail.com>]

On Tue, Jul 20, 2021 at 12:23 PM fengchengwen <fengchengwen@huawei.com> wrote:
>
> Thanks Jerin, comment inline
>
> On 2021/7/20 13:03, Jerin Jacob wrote:
> > On Tue, Jul 20, 2021 at 6:48 AM Chengwen Feng <fengchengwen@huawei.com> wrote:
> >>
> >> This patch introduce 'dmadevice' which is a generic type of DMA
> >> device.
> >>
> >> The APIs of dmadev library exposes some generic operations which can
> >> enable configuration and I/O with the DMA devices.
> >>
> >> Signed-off-by: Chengwen Feng <fengchengwen@huawei.com>
>
> [snip]
>
> >> +int
> >> +rte_dmadev_info_get(uint16_t dev_id, struct rte_dmadev_info *dev_info)
> >> +{
> >> +       const struct rte_dmadev *dev = &rte_dmadevices[dev_id];
> >> +       int ret;
> >> +
> >> +       RTE_DMADEV_VALID_DEV_ID_OR_ERR_RET(dev_id, -EINVAL);
> >> +       if (dev_info == NULL)
> >> +               return -EINVAL;
> >> +
> >> +       RTE_FUNC_PTR_OR_ERR_RET(*dev->dev_ops->dev_info_get, -ENOTSUP);
> >> +       memset(dev_info, 0, sizeof(struct rte_dmadev_info));
> >> +       ret = (*dev->dev_ops->dev_info_get)(dev, dev_info,
> >> +                                           sizeof(struct rte_dmadev_info));
> >> +       if (ret != 0)
> >> +               return ret;
> >> +
> >> +       dev_info->device = dev->device;
> >> +       dev_info->nb_vchans = dev->data->dev_conf.max_vchans;
> >
> > This will be updated after configure stage.
>
> Yes, the dev_info->nb_vchans hold the number of virtual DMA channel configured.
> Do you mean add one comment here ?

If are taking care of the case where rte_dmadev_info_get() called
first and then configure() then fine.


>
> >
> >
> >> +
> >> +       return 0;
> >> +}
> >> +
> >> +int
> >> +rte_dmadev_configure(uint16_t dev_id, const struct rte_dmadev_conf *dev_conf)
> >> +{
> >> +       struct rte_dmadev *dev = &rte_dmadevices[dev_id];
> >> +       struct rte_dmadev_info info;
> >> +       int ret;
> >> +
> >> +       RTE_DMADEV_VALID_DEV_ID_OR_ERR_RET(dev_id, -EINVAL);
> >> +       if (dev_conf == NULL)
> >> +               return -EINVAL;
> >> +
> >> +       ret = rte_dmadev_info_get(dev_id, &info);
> >> +       if (ret != 0) {
> >> +               RTE_DMADEV_LOG(ERR, "Device %u get device info fail\n", dev_id);
> >> +               return -EINVAL;
> >> +       }
> >> +       if (dev_conf->max_vchans == 0) {
> >> +               RTE_DMADEV_LOG(ERR,
> >> +                       "Device %u configure zero vchans\n", dev_id);
> >> +               return -EINVAL;
> >> +       }
> >> +       if (dev_conf->max_vchans > info.max_vchans) {
> >> +               RTE_DMADEV_LOG(ERR,
> >> +                       "Device %u configure too many vchans\n", dev_id);
> >> +               return -EINVAL;
> >> +       }
> >> +       if (dev_conf->enable_silent &&
> >> +           !(info.dev_capa & RTE_DMADEV_CAPA_SILENT)) {
> >> +               RTE_DMADEV_LOG(ERR, "Device %u don't support silent\n", dev_id);
> >> +               return -EINVAL;
> >> +       }
> >> +
> >> +       if (dev->data->dev_started != 0) {
> >> +               RTE_DMADEV_LOG(ERR,
> >> +                       "Device %u must be stopped to allow configuration\n",
> >> +                       dev_id);
> >> +               return -EBUSY;
> >> +       }
> >
> > ethdev and other device class common code handles the reconfigure case. i.e
> > the application configures N vchan first and reconfigures to N - M
> > then free the resources
> > attached to M - N. Please do the same here.
>
> DMA is a simple device, I think it's OK to reconfigure at driver-level.

OK. If everyone thinks that way it is OK. No strong opinion.

>
> PS: If we need support reconfigure at dmadev-level, dmadev should hold the vchan-configuration,
> and invoke driver's vchan_release to release resources. This may introduce more complexity.
>
>
> >> +int
> >> +rte_dmadev_dump(uint16_t dev_id, FILE *f)
> >> +{
> >> +       const struct rte_dmadev *dev = &rte_dmadevices[dev_id];
> >> +       struct rte_dmadev_info info;
> >> +       int ret;
> >> +
> >> +       RTE_DMADEV_VALID_DEV_ID_OR_ERR_RET(dev_id, -EINVAL);
> >> +       if (f == NULL)
> >> +               return -EINVAL;
> >> +
> >> +       ret = rte_dmadev_info_get(dev_id, &info);
> >> +       if (ret != 0) {
> >> +               RTE_DMADEV_LOG(ERR, "Device %u get device info fail\n", dev_id);
> >> +               return -EINVAL;
> >> +       }
> >> +
> >> +       fprintf(f, "DMA Dev %u, '%s' [%s]\n",
> >> +               dev->data->dev_id,
> >> +               dev->data->dev_name,
> >> +               dev->data->dev_started ? "started" : "stopped");
> >> +       fprintf(f, "  dev_capa: 0x%" PRIx64 "\n", info.dev_capa);
> >> +       fprintf(f, "  max_vchans_supported: %u\n", info.max_vchans);
> >> +       fprintf(f, "  max_vchans_configured: %u\n", info.nb_vchans);
> >> +       fprintf(f, "  silent_mode: %s\n",
> >> +               dev->data->dev_conf.enable_silent ? "on" : "off");
> >
> > Probably iterate over each vchan and dumping the at least direction
> > will be usefull.
>
> dmadev hasn't hold vchan-configuration, Need more discussion.

Prefer to have that. Leaving to others.

>