Hi Wolfram, sorry for my late reply. I was on vacation. On Mon, Sep 03, 2018 at 07:21:48PM +0200, Wolfram Sang wrote: > > > Then I vote for extending the 'struct i2c_algorithm' with an extra > > callback 'master_xfer_irqless'. The idea was already proposed here. > > Yes, I proposed the idea a few times and now I cooked up an RFC. > Only build tested and merely a starter for discussion. > > Let me know what you think, people. > > === > > From: Wolfram Sang <wsa@xxxxxxxxxxxxx> > Subject: [RFC PATCH] i2c: introduce master_xfer_irqless callback > > We had the request to access devices very late when interrupts are not > available anymore multiple times now. Mostly to prepare shutdown or > 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. > > Signed-off-by: Wolfram Sang <wsa@xxxxxxxxxxxxx> > --- > drivers/i2c/i2c-core-base.c | 6 +++++- > include/linux/i2c.h | 10 +++++++--- > 2 files changed, 12 insertions(+), 4 deletions(-) I'm fine with this RFC patch (modulo the missing 'master_xfer_irqless != NULL' check already pointed out). It solves my usecase for I2C poweroff/reboot handlers. > 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. I'm now also on your side for this behaviour and not failing with "-EOPNOTSUPP". Explicitly breaking existing code, even if it only worked by chance, is bad, since it will only fail at runtime on a user machine or device. Kind regards, Stefan Lengfeld
