On Wed, Aug 03, 2016 at 10:39:55AM -0700, Bjorn Andersson wrote: > On Tue 02 Aug 00:41 PDT 2016, Luis R. Rodriguez wrote: > > > On Tue, Aug 02, 2016 at 08:53:55AM +0200, Daniel Wagner wrote: > > > On 08/02/2016 08:34 AM, Luis R. Rodriguez wrote: > > > >On Tue, Aug 02, 2016 at 07:49:19AM +0200, Daniel Wagner wrote: > > > >>>The sysdata API's main goal rather is to provide a flexible API first, > > > >>>compartamentalizing the usermode helper was secondary. But now it seems > > > >>>I may just also add devm support too to help simplify code further. > > > >> > > > >>I missed the point that you plan to add usermode helper support to > > > >>the sysdata API. > > > > > > > >I had no such plans, when I have asked folks so far about "hey are you > > > >really in need for it, OK what for? " and "what extended uses do you > > > >envision?" so I far I have not gotten any replies at all. So -- instead > > > >sysdata currently ignores it. > > > > > > So you argue for the remoteproc use case with 100+ MB firmware that > > > if there is a way to load after pivot_root() (or other additional > > > firmware partition shows up) then there is no need at all for > > > usermode helper? > > > > No, I'm saying I'd like to hear valid uses cases for the usermode helper and so > > far I have only found using coccinelle grammar 2 explicit users, that's it. My > > patch series (not yet merge) then annotates these as valid as I've verified > > through their documentation they have some quirky requirement. > > > > I think we're on the same page, but just to make sure; I do not want the > usermode helper, Yay. > I only want a way to wait for the firmware files to > become available. Sure. > > Other than these two drivers I'd like hear to valid requirements for it. > > > > The existential issue is a real issue but it does not look impossible to > > resolve. It may be a solution to bloat up the kernel with 100+ MB size just to > > stuff built-in firmware to avoid this issue, but it does not mean a solution > > is not possible. > > > > Remind me -- why can remoteproc not stuff the firmware in initramfs ? > > > > RAM usage: > Storing the files in initramfs would consume 100MB RAM, we would then > allocate 100MB RAM for buffers during firmware loading and then we have > the reserved 100MB for the peripherals. The buffers could be easily be > removed with a mechanism for providing a buffer to the load operation, > but we would still double the RAM consumption. > > Boot time: > Enlarging the kernel by 100MB will give noticeable addition to boot > times. Right I see.. Since we read the full kernel... > Development issues: > I have numerous concerns related to this, e.g. not being able to side > load the firmware files without rebuilding the initramfs. But most of > these are not technical issues, but rather a matter of convenience. > > One large issue would be how to figure out how large to make the boot > partition in your Android phone, to cope with potential future growth in > firmware size - which has already proven to be a mess. > > Legal matters: > Some of these firmware files are not redistributable, making it > impossible for end users to rebuild their kernel without loosing > functionality. There are even cases where these files are not allowed to > share partition with GPL binaries. > > > Most of these are just a major inconveniences to the developer but some > are show stoppers; especially the legal matters. So if we wave this off > as something people can live without then every downstream will sit on > their own solution to reimplement it. Thanks I'll document these into the firmware_class. > > Anyway, here's a simple suggestion: fs/exec.c gets a sentinel file monitor > > support per enum kernel_read_file_id. For instance we'd have one for > > READING_FIRMWARE, one for READING_KEXEC_IMAGE, perhaps READING_POLICY, and this > > would in turn be used as the system configurable deterministic file for > > which to wait for to be present before enabling each enum kernel_read_file_id > > type read. > > > > Thoughts ? > > That does sound like a good generic solution for our problem and for the > other types of files as well. Do you have any ideas (patches?) on how > each sentinel would be triggered? > > The only concern I can think of right now is that the > firmware_class.path might point to a separate partition; but based on > how the signaling of the sentinels are implemented this might not be an > issue. There's another simpler suggestion I'm getting too, will post in the other thread. Luis -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
