On Fri, 2005-09-30 at 16:32 -0400, Luben Tuikov wrote: > On 09/30/05 16:14, Andrew Patterson wrote: > > > > Yes you can, which is what I am trying to do. However, is that library > > also available on Solaris and Windows? Is it up to date? These are the > > Is the kernel the latest one? Is it up to date? > > See? Same argument. > > >>>Note that a sysfs implementation has problems. Binary attributes are > >>>discouraged/not-allowed. > >> > >>I've never heard that. Is this similar to the argument > >>"The sysfs tree would be too deep?" > > > > > >>From Documentation/filesystes/sysfs.txt > > > > "Attributes should be ASCII text files, preferably with only one value > > per file. It is noted that it may not be efficient to contain only > > value per file, so it is socially acceptable to express an array of > > values of the same type. > > > > Mixing types, expressing multiple lines of data, and doing fancy > > formatting of data is heavily frowned upon. Doing these things may get > > you publically humiliated and your code rewritten without notice." > > I see this talk _only_ about non-binary attributes. I think that "ASCII text files" implies non-binary. As Willy has pointed out, this has already been violated. > > Plus you have to admit: the SAS sysfs "smp_portal" binary > attribute is very versatile: you completely control the > expander from user space _if_ you can see it: It is > almost like "point and click". No problem with this. > > I imagine there would be GUIs built on top of it, which would > actually implement that "point, click, control". > > > My understanding is that sysfs is meant to be human-readable. I do not > > But `cat /sysfs/.../smp_portal` _is_ human readable. See? Its size is > 0 bytes and when you read it you get 0 data read. I don't quite think your definition of human readable is the same as mine. I think the intention is to do something like: $ cat attribute 3 Gb/s or $ echo "3 Gb/s" >attribute Rather than $ cat attribute gibberish. or $ echo "gibberish" >attribute But again, this may be just a goal and not a hard and fast rule. I can definitely see a use for binary attributes in sysfs. Configfs seems to be designed for this sort of thing. > > > User space locking can only guarantee atomic operations in user space. > > And user space is the whole audience of this interface. > > > Not sure at the moment, can I guarantee this for the future? > > How far in the future? 1, 3, 6 months? 1, 3, 6 years? > Plus if you need an attribute larger than 4K, you've got > other problems to worry about. > > > There are as many as one would want. We now have 32 bit device numbers. > > Old technology is fine as long as it works, especially if their is no > > new technology to replace it. Note that I don't like the character > > device solution either. What would really be nice is something that will > > allow us to pass an arbitrary request buffer, and get an arbitrary > > response buffer back in a single transaction, > , locks it, then hangs. > Here: > > /* User space lock */ > > fd = open(smp_portal, ...); > write(fd, smp_req, smp_req_size); > read(fd, smp_resp, smp_resp_size); > close(fd); > > /* User space unlock */ > > > See above. This stuff works for trivial user-space apps. It will not > > suffice for most storage management apps. > > Sorry but I completely fail to see this argument., locks it, then hangs. > > How will it "fail for most storage managament apps"? Let's see, one example: Process A opens an attribute and writes to it. Process B opens another attribute and writes to it, affecting the result that process A will see from its subsequent read. I suppose you could lock every attribute, but that would be very error-prone, and not allow much concurrency. Andrew > > Luben > - : send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
