Messages in this thread | | | Date | Fri, 29 Aug 2014 14:43:13 -0400 | From | Chris Metcalf <> | Subject | Re: [PATCH 2/5] char: tile-srom: Remove reference to platform_bus |
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(Resending with text/plain.)
First, sorry for the delayed response, with summer vacation and then trying to catch up. :-)
On 8/8/2014 12:34 PM, Pawel Moll wrote: > On Tue, 2014-08-05 at 21:08 +0100, Chris Metcalf wrote: >>>> In addition, we also have user binaries >>>> in the wild that know to look for /sys/devices/platform/srom/ paths, >>>> so I'm pretty reluctant to change this path without good reason. >>> So what is the srom class for then if not for device discovery? And why >>> do they look for them in the first place? To get relevant character >>> device's data, if I understand it right? >>> >>> Maybe you could just register a simple "proper" platform device for all >>> the sroms and then hang the class devices from it? I can type some code >>> doing this if it sound reasonably? >> By "device discovery" I meant the way you find the way in your devices >> in /sysfs. You seem to be traversing /sys/devices/... tree, while you've >> got almost direct access to them through /sys/class/srom and you can (I >> believe, correct me if I'm wrong, Greg) rely on this path being stable.
Yes, this is an excellent point. I will change the user tool to use /sys/class instead and then it will work with the existing kernel as well as with future kernels that incorporate your suggested change.
>> The >> subdirectories under /sys/devices/platform/srom/ correspond to partitions >> in the SPI-ROM, which are software constructs created by the Tilera hypervisor. >> By default we have three, where the first holds boot data that the chip >> can use to boot out of hardware, and the other two are smaller partitions >> for boot- and user-specific data. We use the /sys files primarily to get the >> page size and sector size for the sroms, and also export other interesting >> information like the total size of the particular srom device. >> >> Thank you for volunteering to write a bit of code; if that's the best >> way to clarify this for us, fantastic, or else pointing us at existing >> good practices or documentation would be great too. > [...] > @@ -350,7 +351,7 @@ static int srom_setup_minor(struct srom_dev *srom, int index) > SROM_PAGE_SIZE_OFF, sizeof(srom->page_size)) < 0) > return -EIO; > > - dev = device_create(srom_class, &platform_bus, > + dev = device_create(srom_class, srom_parent, > MKDEV(srom_major, index), srom, "%d", index); > return PTR_ERR_OR_ZERO(dev); > }
The second argument should be &srom_parent.dev though, I think. Right?
> Would that work for you? Note that it will move the srom class devices > one level deeper in /sys/devices/... hierarchy.
Yes, that seems slightly unfortunately but not too problematic. If the consensus is that this is the way to go, I can certainly take this change into the Tile tree.
-- Chris Metcalf, Tilera Corp. http://www.tilera.com
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