Hi, > From: linux-acpi-owner@xxxxxxxxxxxxxxx [mailto:linux-acpi-owner@xxxxxxxxxxxxxxx] On Behalf Of Matthew Garrett > Sent: Saturday, February 22, 2014 12:13 AM > > On Fri, 2014-02-21 at 02:17 +0000, Zheng, Lv wrote: > > > In fact there is a workaround solution I've posted here: > > https://patchwork.kernel.org/patch/2831851/ > > The updated version of this patch can be found at: > > https://bugzilla.kernel.org/attachment.cgi?id=112611 > > It is the acpi-ipmi13.patch file. > > I don't think that solves the underlying problem? We're still left with > no guarantee of ordering between ACPI IPMI operation region support > being available and the loading of a driver that may rely on it. Yes. As it is a bit far beyond the bug report, I didn't work on it. But actually, I have solution to achieve this. > > I think there should be relationship between ACPI region and Linux kernel modules. > > In fact on the well-known operating system, _REG is always invoked at the end of the IRP_PNP_START_DEVICE completions. > > But we may still be able to return -EPROBE_DEFER in the power meter driver when it detects failures caused by the readiness state > of the region handlers. > > We don't have a guarantee that it'll happen at probe time. The > capabilities list may be static, and so we'll get our first failure on > an attempted userspace access instead. This is the issue related to the IPMI operation region, and it can be solved by a "request_module()" call. The -EPROBE_DEFER I mentioned is about the quality of acpi power meter driver itself. > It may be that Corey's suggestion satisfies the concerns Russ raised. > Building IPMI in but only probing by default on systems that declare a > BMC in ACPI or DMI should avoid boot-time delays while still ensuring > that the functionality is available on systems where there's a real > chance that the firmware expects the OS to provide support. If you take a look at this patch (https://patchwork.kernel.org/patch/2831851/), you'll see it is possible to add request_module() in acpi_region_default_handler(). The callback is invoked when the first IPMI region access happens and it is in the process context without any locking. I'd rather to embed acpi_ipmi into ipmi_si module with this fix: https://bugzilla.kernel.org/attachment.cgi?id=112611 (acpi-ipmi14.patch). After that, a request_module() invocation of ipmi_si in acpi_region_default_handler() can solve what you are worrying about. What's your opinion? Thanks and best regards -Lv > -- > Matthew Garrett <matthew.garrett@xxxxxxxxxx> ��.n��������+%������w��{.n�����{�����ܨ}���Ơz�j:+v�����w����ޙ��&�)ߡ�a����z�ޗ���ݢj��w�f
