On Fri, Feb 15, 2019 at 08:57:27PM +0800, Hsin-Yi Wang wrote: > On Fri, Feb 15, 2019 at 5:25 PM Wolfram Sang <wsa@xxxxxxxxxxxxx> wrote: > > > > On Fri, Feb 15, 2019 at 05:17:27PM +0800, Hsin-Yi Wang wrote: > > > Ok, I can add a check in another patch. Should we return NULL pointer > > > if msg->len is 0 or print out some warnings? Thanks. > > > > No warning, msg->len == 0 is a valid setting. But interesting question: > > I was about to say NULL, but your driver would assume ENOMEM there and > > discard the message which is also not correct since msg->len == 0 is a > > valid setting. So, should we just return msg->buf then? Will this work > > with your driver? Can it handle zero-length transfers? > > dma_map_single(i2c->dev, msg->buf , msgs->len, DMA_TO_DEVICE); breaks > kernel if msgs->len is 0, so I think it doesn't handle zero-length transfer. Please don't drop the i2c list. Then, the correct solution for your driver is to forbid those transfers with this controller. Check I2C_AQ_NO_ZERO_LEN. Also, update the functionality like this I2C_FUNC_SMBUS_EMUL & ~I2C_FUNC_SMBUS_QUICK.
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