On 05-07-21, 14:22, Jie Deng wrote: > On 2021/7/5 12:38, Viresh Kumar wrote: > > On 05-07-21, 11:45, Jie Deng wrote: > > > On 2021/7/5 10:40, Viresh Kumar wrote: > > > > On 02-07-21, 16:46, Jie Deng wrote: > > > > The right way of doing this is is making this function return - Error on failure > > > > and 0 on success. There is no point returning number of successful additions > > > > here. > > > > > > We need the number for virtio_i2c_complete_reqs to do cleanup. We don't have > > > to > > > > > > do cleanup "num" times every time. Just do it as needed. > > If you do full cleanup here, then you won't required that at the caller site. > > > > > > Moreover, on failures this needs to clean up (free the dmabufs) itself, just > > > > like you did i2c_put_dma_safe_msg_buf() at the end. The caller shouldn't be > > > > required to handle the error cases by freeing up resources. > > > > > > This function will return the number of requests being successfully prepared > > > and make sure > > > > > > resources of the failed request being freed. And virtio_i2c_complete_reqs > > > will free the > > > > > > resources of those successful request. > > It just looks cleaner to give such responsibility to each and every function, > > i.e. if they fail, they should clean stuff up instead of the caller. That's the > > normal philosophy you will find across kernel in most of the cases. > > > > > + /* > > > > > + * Condition (req && req == &reqs[i]) should always meet since > > > > > + * we have total nr requests in the vq. > > > > > + */ > > > > > + if (!failed && (WARN_ON(!(req && req == &reqs[i])) || > > > > > + (req->in_hdr.status != VIRTIO_I2C_MSG_OK))) > > > > What about writing this as: > > > > > > > > if (!failed && (WARN_ON(req != &reqs[i]) || > > > > (req->in_hdr.status != VIRTIO_I2C_MSG_OK))) > > > > > > > > We don't need to check req here since if req is NULL, we will not do req->in_hdr > > > > at all. > > > > > > It's right here just because the &reqs[i] will never be NULL in our case. > > > But if you see > > > > > > "virtio_i2c_complete_reqs" as an independent function, you need to check the > > > > > > req. From the perspective of the callee, you can't ask the caller always > > > give you > > > > > > the non-NULL parameters. > > We need to keep this driver optimized in its current form. If you see your own > > argument here, then why don't you test vq or msgs for a valid pointer ? And even > > reqs. > > > > If we know for certain that this will never happen, then it should be optimized. > > But if you see a case where reqs[i] can be NULL here, then it would be fine. > > ot the driver. And we don't need to take care of that. > > > This is still not enough to convince me. So I won't change them for now > until I see it > > is the consensus of the majority. Do you see reqs[i] to ever be NULL here ? If not, then if (req) is like if (true). Why would you want to have something like that ? -- viresh
