On Wed, Nov 21, 2012 at 8:48 PM, Simon Glass <s...@chromium.org> wrote: > Hi Grant, > > On Wed, Nov 21, 2012 at 7:47 AM, Grant Likely <grant.lik...@secretlab.ca> > wrote: >> On Tue, 20 Nov 2012 15:48:24 -0800, Simon Glass <s...@chromium.org> wrote: >>> Hi Grant, >>> >>> On Tue, Nov 20, 2012 at 2:32 PM, Grant Likely <grant.lik...@secretlab.ca> >>> wrote: >>> > On Tue, Nov 20, 2012 at 10:23 PM, Simon Glass <s...@chromium.org> wrote: >>> >> Hi, >>> >> >>> >> I hope this is a stupid question with an easy answer, but I cannot find >>> >> it. >>> >> >>> >> I have a device tree node for an mmc block device and I want to use >>> >> that block device from another driver. I have a phandle which lets me >>> >> get the node of the mmc device, but I am not sure how to convert that >>> >> into a block_device. In order to do so, I think I need a major/minor >>> >> number. Of course the phandle might in fact point to a SCSI driver and >>> >> I want that to work correctly also. >>> >> >>> >> I imagine I might be able to search through the wonders of sysfs in >>> >> user space, but is there a better way? >>> > >>> > Do you /want/ to do it from userspace? What is your use case? Mounting >>> > the rootfs? >>> >>> The use case is storing some raw data on a block device from within a >>> driver in the kernel. It is used to keep track of the verified boot >>> state. >>> >>> > >>> > Regardless, userspace can monitor the uevents when devices are added >>> > (that's what udev does) and watch for the full path of the node you >>> > want in the uevent attribute. Then you can look for the child device >>> > with the block major/minor numbers in it. >>> >>> So is there a way to do this entirely in the kernel ex post? It might >>> need to happen during kernel boot, before user space. >> >> Yes, it is certainly doable within the kernel. First, you'll need to use >> a notifier to get called back whenever a new device is created. Then >> you'll need to look at the dev->of_node(->full_name) to see if it is the >> node you actually want. You might need/want to resolve it from an alias >> or something, but I presume you already have a way to find the >> device_node before seaching for a struct device. > > OK thank you. Was hoping to find a simple way to find a block device > from a device tree node (yes I know the right one) but I suppose in > general this is impossible, since nodes may create more than one > device, and each has its own data structures leading to the block > device. > > So it seems like a notifier is the best way. Thanks for looking at this Grant.
It's certainly the least invasive way. Otherwise you need to hook into the DT device creation code. g. -- Grant Likely, B.Sc., P.Eng. Secret Lab Technologies Ltd. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
