Messages in this thread | | | Date | Mon, 25 Jan 2016 11:30:42 -0800 | From | Brian Norris <> | Subject | Re: [PATCH] mtd: bcm47xxsflash: use ioremap_cachable() instead of KSEG0ADDR() |
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On Mon, Jan 25, 2016 at 07:15:49PM +0000, Maciej W. Rozycki wrote: > On Mon, 25 Jan 2016, Brian Norris wrote: > > > > > + res = platform_get_resource(pdev, IORESOURCE_MEM, 0); > > > > + if (!res) { > > > > + dev_err(dev, "invalid resource\n"); > > > > + return -EINVAL; > > > > + } > > > > + if (!devm_request_mem_region(dev, res->start, resource_size(res), > > > > + res->name)) { > > > > + dev_err(dev, "can't request region for resource %pR\n", res); > > > > + return -EBUSY; > > > > + } > > > > + b47s->window = ioremap_cachable(res->start, resource_size(res)); > > > > + if (!b47s->window) { > > > > + dev_err(dev, "ioremap failed for resource %pR\n", res); > > > > > > You need to call `devm_release_mem_region' in this case. > > > > No he doesn't. devm_* functions automatically release their resources > > when either the device is removed, or the probe() fails. So the whole > > point is that we don't have to explicitly manage the error case. > > Why does `devm_ioremap_resource' (in lib/devres.c) do that manually then? > > dest_ptr = devm_ioremap(dev, res->start, size); > if (!dest_ptr) { > dev_err(dev, "ioremap failed for resource %pR\n", res); > devm_release_mem_region(dev, res->start, size); > dest_ptr = IOMEM_ERR_PTR(-ENOMEM); > } > > Is this an oversight or was it a deliberate design decision?
I didn't design it, but I suspect it's because the API for devm_ioremap_resource() doesn't assume that a failed devm_ioremap_resource() means probe() will exit. Perhaps the driver will have some alternative action instead. It's still good to release the resources implicitly requested by devm_ioremap_resource().
The difference for us is that we *know* we're exiting the probe(), so we can rely on the automatic cleanup.
> > But...since he's not using a devm_* version of ioremap (there isn't one > > for ioremap_cachable()), we actually need to add an iounmap() for the > > case where mtd_device_parse_register() fails. If we fix that one, I can > > apply this. > > As from 4.5-rc1 we now have `ioremap_cache' available for MIPS as well > (thanks, Ralf, for a quick action on that!), so you can use that instead > to make your code generic.
OK, but there's still not a devm_* version of ioremap_cache(), so we'd still need to do the iounmap() ourselves.
Also, it looks like kernel/memremap.c is suggesting we use memremap() instead of ioremap_cache()... But I'm not sure if that's really what we want.
Brian
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