On 2018-09-20 18:14, Wolfram Sang wrote: > We had the request to access devices very late when interrupts are not > available anymore multiple times now. Mostly to prepare shutdown or
The first sentence is a bit backwards, I'd rephrase like so: Multiple times now we've had the request to access devices very late, when interrupts are no longer available. > reboot. Allow adapters to specify a specific callback for this case. > Note that we fall back to the generic master_xfer callback if this new > irqless one is not present. This is intentional to preserve the previous > behaviour and avoid regressions. Because there are drivers not using > interrupts or because it might have worked "accidently" before. accidentally > > Signed-off-by: Wolfram Sang <[email protected]> > --- > drivers/i2c/i2c-core-base.c | 6 +++++- > include/linux/i2c.h | 10 +++++++--- > 2 files changed, 12 insertions(+), 4 deletions(-) > > diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c > index 904b4d2ebefa..f827446c3089 100644 > --- a/drivers/i2c/i2c-core-base.c > +++ b/drivers/i2c/i2c-core-base.c > @@ -1887,7 +1887,11 @@ int __i2c_transfer(struct i2c_adapter *adap, struct > i2c_msg *msgs, int num) > /* Retry automatically on arbitration loss */ > orig_jiffies = jiffies; > for (ret = 0, try = 0; try <= adap->retries; try++) { > - ret = adap->algo->master_xfer(adap, msgs, num); > + if ((in_atomic() || irqs_disabled()) && > adap->algo->master_xfer_irqless) > + ret = adap->algo->master_xfer_irqless(adap, msgs, num); > + else > + ret = adap->algo->master_xfer(adap, msgs, num); > + > if (ret != -EAGAIN) > break; > if (time_after(jiffies, orig_jiffies + adap->timeout)) > diff --git a/include/linux/i2c.h b/include/linux/i2c.h > index 65b4eaed1d96..11e615123bd0 100644 > --- a/include/linux/i2c.h > +++ b/include/linux/i2c.h > @@ -498,6 +498,8 @@ i2c_register_board_info(int busnum, struct i2c_board_info > const *info, > * @master_xfer: Issue a set of i2c transactions to the given I2C adapter > * defined by the msgs array, with num messages available to transfer via > * the adapter specified by adap. > + * @master_xfer_irqless: same as master_xfer. Yet, not using any interrupts "Same" (with capital 'S') to match the other entries. Also, should it not be @master_xfer to help the tools do the right thing? > + * so e.g. PMICs can be accessed very late before shutdown Trailing period. I'm fine with this change, but should it not wait until there is a user? (I think there is one in the wings, so that's a very weak objection...) Acked-by: Peter Rosin <[email protected]> > * @smbus_xfer: Issue smbus transactions to the given I2C adapter. If this > * is not present, then the bus layer will try and convert the SMBus calls > * into I2C transfers instead. > @@ -511,9 +513,9 @@ i2c_register_board_info(int busnum, struct i2c_board_info > const *info, > * be addressed using the same bus algorithms - i.e. bit-banging or the > PCF8584 > * to name two of the most common. > * > - * The return codes from the @master_xfer field should indicate the type of > - * error code that occurred during the transfer, as documented in the kernel > - * Documentation file Documentation/i2c/fault-codes. > + * The return codes from the @master_xfer{_irqless} field should indicate the > + * type of error code that occurred during the transfer, as documented in the > + * Kernel Documentation file Documentation/i2c/fault-codes. > */ > struct i2c_algorithm { > /* If an adapter algorithm can't do I2C-level access, set master_xfer > @@ -524,6 +526,8 @@ struct i2c_algorithm { > processed, or a negative value on error */ > int (*master_xfer)(struct i2c_adapter *adap, struct i2c_msg *msgs, > int num); > + int (*master_xfer_irqless)(struct i2c_adapter *adap, > + struct i2c_msg *msgs, int num); > int (*smbus_xfer) (struct i2c_adapter *adap, u16 addr, > unsigned short flags, char read_write, > u8 command, int size, union i2c_smbus_data *data); >
