| Message ID | 1360953682-25066-1-git-send-email-dianders@chromium.org |
|---|---|
| State | Rejected |
| Headers | show |
On Fri, Feb 15, 2013 at 10:41:22AM -0800, Doug Anderson wrote: > Stephen Warren pointed out as part of a code review of another mux > driver that there should be no need to have > "platform_set_drvdata(pdev, NULL)" in the remove function. Get rid of > it in the i2c-mux-gpio driver. > > See Stephen's comment at: > http://www.gossamer-threads.com/lists/linux/kernel/1678627?do=post_view_threaded#1678627 > > Signed-off-by: Doug Anderson <dianders@chromium.org> I think we should do this at least I2C subsystem wide (51 occasions of setting some *_drvdata to NULL), even better kernel-wide. Patching individual drivers won't cut the confusion around this issue, I am afraid. Thanks, Wolfram -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Wolfram, On Fri, Feb 15, 2013 at 11:37 AM, Wolfram Sang <wsa@the-dreams.de> wrote: > I think we should do this at least I2C subsystem wide (51 occasions of > setting some *_drvdata to NULL), even better kernel-wide. Patching > individual drivers won't cut the confusion around this issue, I am > afraid. I did it "mux" directory wide and this was the only instance. ;) I'll re-send with I2C subsystem wide. I probably won't attempt the whole kernel wide at this point, but would be very happy if someone else wanted to! :) Thanks for the review! -Doug -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
> I'll re-send with I2C subsystem wide. I probably won't attempt the > whole kernel wide at this point, but would be very happy if someone > else wanted to! :) Thanks. Please double check that setting NULL is really unneeded for the non-platform-bus variants, too, or skip those if you are unsure. Please also update the commit message to reference a stronger indication than Stephen's "should not be necessary" ;) I do agree but for the commit history, a better reference would be nice to educate readers. Thanks, Wolfram -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Wolfram, On Fri, Feb 15, 2013 at 11:53 AM, Wolfram Sang <wsa@the-dreams.de> wrote: > >> I'll re-send with I2C subsystem wide. I probably won't attempt the >> whole kernel wide at this point, but would be very happy if someone >> else wanted to! :) > > Thanks. Please double check that setting NULL is really unneeded for the > non-platform-bus variants, too, or skip those if you are unsure. Please > also update the commit message to reference a stronger indication than > Stephen's "should not be necessary" ;) I do agree but for the commit > history, a better reference would be nice to educate readers. Sounds good. I've it looks like non-platform-bus instances in drivers/i2c break down to: * dev_set_drvdata() directly (even though we're a platform device) * pci_set_drvdata() * amba_set_drvdata() * serio_set_drvdata() I'll go ahead and include those in my patch. I've looked through the code a bit. While I can't 100% guarantee that there's not some strange code path that I'm missing, it all looks pretty straightforward. A few points to be made: * It would be a bit hard to believe that some higher-level code could make any particular assumptions about the value in the pointer (it might point to static data, kmalloced data, etc). ...so if the higher-level code is directly looking at this value it'd really could only be looking to validate that the driver put NULL here. I don't see that anywhere. * I've checked all of the calls to xxx_get_drvdata() in the drivers touched. The majority are in remove, suspend, or resume, so we're good there. In other cases I just validated that they aren't checking for and relying on a NULL result of xxx_get_drvdata(). * It would be possible that some subsystem tries to be helpful and call xxx_get_drvdata() for you and then pass drvdata into a callback (so I wouldn't see xxx_get_drvdata()). I don't see that (it would be a strange design anyway IMHO). Most of the time I2C devices seem to get their private data from adap->algo_data anyway (or from the pointer passed to IRQ registration) and xxx_set_drvdata() doesn't touch those. * The __device_release_driver() function actually calls the "dev_set_drvdata(dev, NULL)" for you anyway. ...and I that's what's running the remove code anyway. ...so we'd only need to worry about code that could show up before that... -Doug -- To unsubscribe from this list: send the line "unsubscribe linux-i2c" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/drivers/i2c/muxes/i2c-mux-gpio.c b/drivers/i2c/muxes/i2c-mux-gpio.c index 9f50ef0..abc2e55a 100644 --- a/drivers/i2c/muxes/i2c-mux-gpio.c +++ b/drivers/i2c/muxes/i2c-mux-gpio.c @@ -250,7 +250,6 @@ static int i2c_mux_gpio_remove(struct platform_device *pdev) for (i = 0; i < mux->data.n_gpios; i++) gpio_free(mux->gpio_base + mux->data.gpios[i]); - platform_set_drvdata(pdev, NULL); i2c_put_adapter(mux->parent); return 0;
Stephen Warren pointed out as part of a code review of another mux driver that there should be no need to have "platform_set_drvdata(pdev, NULL)" in the remove function. Get rid of it in the i2c-mux-gpio driver. See Stephen's comment at: http://www.gossamer-threads.com/lists/linux/kernel/1678627?do=post_view_threaded#1678627 Signed-off-by: Doug Anderson <dianders@chromium.org> --- drivers/i2c/muxes/i2c-mux-gpio.c | 1 - 1 file changed, 1 deletion(-)