> Well, it does not block but passing -EAGAIN directly back is not nice. > Or does the hw_random framework handle this?
The framework is passing -EAGAIN to userspace which isn't very nice at all. Luckily, handling it is pretty trival so I went ahead and made an updated patch to address this. (I'm unsure of how to submit an update to my patch so I'll need a bit of guidence on this.) > Maybe our -EAGAIN handling is buggy. > That said I'm all for changing the driver to use the right framework > but please make sure that we don't drop useful stuff like -EAGAIN handling. Most of the old code was pulled from the framework anyway so it's very unlikely that anything else would be dropped here. On Thu, 29 Aug 2019 17:30:59 +0200 (CEST), Richard Weinberger <rich...@nod.at> wrote: > ----- Ursprüngliche Mail ----- > > Von: "Dark" <d...@volatile.bz> > > An: "Richard Weinberger" <richard.weinber...@gmail.com>, "linux-kernel" > > <linux-kernel@vger.kernel.org> > > CC: "richard" <rich...@nod.at>, "anton ivanov" > > <anton.iva...@cambridgegreys.com>, "linux-um" > > <linux...@lists.infradead.org> > > Gesendet: Donnerstag, 29. August 2019 16:36:28 > > Betreff: Re: [PATCH] um: Rewrite host RNG driver. > > > On Thu, 29 Aug 2019 15:26:24 +0200, Richard Weinberger > > <richard.weinber...@gmail.com> wrote: > >> So, you removed -EAGAIN handling, made everything synchronous, > >> and changed the interface.t > >> I'm not sure if this really a much better option. > > > > I should have been more clear here that I'm using the interfaces > > provided by `drivers/char/hw_random/core.c` for consistency with the > > other hardware RNG drivers and to avoid reimplementing stuff that's > > already there. > > I got this, and this is a good thing! > > > It might be a bit hard to see in the diff, but I pass the file > > descriptor to `os_set_fd_async()` to prevent it from blocking. > > Well, it does not block but passing -EAGAIN directly back is not nice. > Or does the hw_random framework handle this? > > > For the -EAGAIN handling, I'm passing it onto the caller. Since you > > mentioned it, It would be better to handle it in the driver itself > > so I'll update the patch to address that. > > > >> Rewriting the driver in a modern manner is a good thing, but throwing the > >> old one way with a little hand weaving just because of a unspecified issue > >> is a little harsh. > >> Can you at lest provide more infos what problem you're facing with the > >> old driver? > > > > Most of it boiled down to it silently breaking if /dev/random on the > > host were to block for any reason, and there was the userspace tool > > requirement to properly make use of it. With that said, the interface > > was also inconsistent with the other hardware RNG drivers which would > > require a rewrite to address anyway. > > Maybe our -EAGAIN handling is buggy. > That said I'm all for changing the driver to use the right framework > but please make sure that we don't drop useful stuff like -EAGAIN handling. > > Thanks, > //richard
