Hi Antony, On Tue, May 05, 2020 at 03:55:06PM +0300, Antony Pavlov wrote: > Here is the code from drivers/reset/reset-socfpga.c > > > res = dev_request_mem_resource(dev, 0); > > data->membase = IOMEM(res->start); > > if (IS_ERR(data->membase)) > > return PTR_ERR(data->membase); > > dev_request_mem_resource(dev, 0) returns res or ERR_CASE(res) > so we can't use IOMEM(res->start) just after > res = dev_request_mem_resource(dev, 0) call. > > Code should look like this > > > res = dev_request_mem_resource(dev, 0); > > if (IS_ERR(res)) > > return PTR_ERR(res); > > data->membase = IOMEM(res->start); > > but if res isn't used in after that we can > use dev_request_mem_region() instead of > dev_request_mem_resource(), e.g. > > > data->membase = dev_request_mem_region(dev, 0); > > if (IS_ERR(data->membase)) > > return PTR_ERR(data->membase); The problem with dev_request_mem_region() is that the returned value leaves no space for error codes. IS_ERR() returns false positives when the returned region is within the last 512 bytes of the address space. This is rare, but has happened. This is why the common pattern is to use dev_request_mem_resource() which can fail and then convert the resource into a pointer, which cannot fail. Sascha -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 | _______________________________________________ barebox mailing list barebox@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/barebox
