On Tuesday 15 January 2019 10:45:55 Jan Kara wrote: > On Tue 15-01-19 09:48:32, Pali Rohár wrote: > > On Tuesday 15 January 2019 09:41:19 Jan Kara wrote: > > > On Tue 15-01-19 09:31:11, Pali Rohár wrote: > > > > On Monday 14 January 2019 19:07:35 Michael Sabolish wrote: > > > > > I can try and make a pull-request for udftune, and I can just copy the API for tune2fs. It would work something like: > > > > > > > > > > udftune -O read-only device (to set read-only access type) > > > > > > > > > > or: > > > > > > > > > > udftune -O ^read-only device (to clear read-only access type (aka set rw)) > > > > > > > > This API is ambiguous. What does it mean for ^read-only? In UDF you have > > > > following access types: overwritable, rewritable, writeonce, readonly, > > > > pseudo-overwritable, unknown. > > > > > > > > So you would need to know to which R/W access type to switch > > > > (overwritable, rewritable, writeonce or pseudo-overwritable). > > > > > > > > With information of media type, you could be able to guess correct > > > > access type. But for UDF images stored in VFS there is no media > > > > information. Also you can have uncommon setup, e.g. usage of CD-R > > > > writeonce setup on CD-R/W disc. So "autodetection" of media type would > > > > not work always correctly. > > > > > > > > So I think that it would be better to have following API: > > > > > > > > udftune --access-type=<new_access_type> > > > > > > > > or > > > > > > > > udftune --change-access-type=<new_access_type> > > > > > > > > I understand that you would like to have similar API as tune2fs, but UDF > > > > settings are too different from ext*. > > > > > > If you wanted to follow tune2fs interface, you can have e.g.: > > > > Question is if it is a good idea to follow this interface. > > Agreed. I'll leave that decision up to you as a maintainer :) > > > > udftune -E access-type=<foo> > > > > > > Another question about the feature is - the access type is actually per > > > partition and there can be multiple partitions on UDF media. So I think we > > > need to specify the partition number in the command and <foo> has to > > > actually be something like <partition number>,<access_type>. > > > > Access type is stored in partition descriptor and in UDF (as opposite of > > ECMA-167) you can have only one partition descriptor. IIRC there is some > > exception when you have two partition descriptors, but then one have to be > > readonly and second virtual. > > Ah, right, I forgot that UDF standard limits how partitions can be set up. > However I don't see anything that would limit number of "type 1" maps? I've > only found in 2.2.4.7 that "Partition Maps shall be limited to Partition > Map type 1, except type 2 maps ...". In which I'm not sure whether this is > meant to imply there is only one 'type 1' partition map or whether there > can be more of them. That is interesting question... I just found following: In section "2. Basic Restrictions & Requirements" there is information about "Partition Descriptor": A Partition Descriptor Access Type of read-only, rewritable, overwritable, write-once and pseudo-overwritable shall be supported. There shall be exactly one prevailing Partition Descriptor recorded per volume, with one exception. For Volume Sets that consist of single volume, the volume may contain 2 non-overlapping Partitions with 2 prevailing Partition Descriptors only if one has an Access Type of read-only and the other has an Access Type of rewritable, overwritable, or write-once. The Logical Volume for this volume would consist of the contents of both partitions. But again it does not answer to your question. -- Pali Rohár pali.rohar@xxxxxxxxx
