Re: [PATCH v3 10/25] bus: mhi: ep: Add support for creating and destroying MHI EP devices

Manivannan Sadhasivam
2022-02-17T12:04:48Z

On Tue, Feb 15, 2022 at 02:02:57PM -0600, Alex Elder wrote:

[...]

> > +
> > + mhi_dev = mhi_ep_alloc_device(mhi_cntrl, MHI_DEVICE_XFER);
> > + if (IS_ERR(mhi_dev))
> > + return PTR_ERR(mhi_dev);
>
> It looks like the only possible error is no memory, so you could
> just have mhi_ep_alloc_device() return NULL.
>

I think returning the actual error is more safe as we may end up adding more
stuff into this function in the future.

> > +
> > + /* Configure primary channel */
> > + mhi_dev->ul_chan = mhi_chan;
> > + get_device(&mhi_dev->dev);
> > + mhi_chan->mhi_dev = mhi_dev;
> > +
> > + /* Configure secondary channel as well */
> > + mhi_chan++;
> > + mhi_dev->dl_chan = mhi_chan;
> > + get_device(&mhi_dev->dev);
> > + mhi_chan->mhi_dev = mhi_dev;
> > +
> > + /* Channel name is same for both UL and DL */
> > + mhi_dev->name = mhi_chan->name;
> > + dev_set_name(&mhi_dev->dev, "%s_%s",
> > + dev_name(&mhi_cntrl->mhi_dev->dev),
> > + mhi_dev->name);
> > +
> > + ret = device_add(&mhi_dev->dev);
> > + if (ret)
> > + put_device(&mhi_dev->dev);
> > +
> > + return ret;
> > +}
> > +
> > +static int mhi_ep_destroy_device(struct device *dev, void *data)
> > +{
> > + struct mhi_ep_device *mhi_dev;
> > + struct mhi_ep_cntrl *mhi_cntrl;
> > + struct mhi_ep_chan *ul_chan, *dl_chan;
> > +
> > + if (dev->bus != &mhi_ep_bus_type)
> > + return 0;
> > +
> > + mhi_dev = to_mhi_ep_device(dev);
> > + mhi_cntrl = mhi_dev->mhi_cntrl;
> > +
> > + /* Only destroy devices created for channels */
> > + if (mhi_dev->dev_type == MHI_DEVICE_CONTROLLER)
> > + return 0;
> > +
> > + ul_chan = mhi_dev->ul_chan;
> > + dl_chan = mhi_dev->dl_chan;
>
> Aren't they required to supply *both* channels? Or maybe
> it's just required that there are transfer callback functions
> for both channels. Anyway, no need to check for null, because
> the creation function guarantees they're both non-null I think.
>

mhi_ep_destroy_device() will be called for each device separately. So we
must check for NULL.

Thanks,
Mani