It does not make any difference. Essentially, a get_handle is performed by evaluate_object anyway. >-----Original Message----- >From: Toshi Kani [mailto:toshi.kani@xxxxxx] >Sent: Tuesday, May 29, 2012 4:43 PM >To: shuahkhan@xxxxxxxxx >Cc: Moore, Robert; lenb@xxxxxxxxxx; linux-acpi@xxxxxxxxxxxxxxx; >bhelgaas@xxxxxxxxxx; liuj97@xxxxxxxxx; andi@xxxxxxxxxxxxxx; linux- >kernel@xxxxxxxxxxxxxxx >Subject: RE: [PATCH v4 0/6] ACPI: Add _OST support for ACPI hotplug > >On Tue, 2012-05-29 at 16:44 -0600, Shuah Khan wrote: >> On Tue, 2012-05-29 at 22:27 +0000, Moore, Robert wrote: >> > > > 2. Calling acpi_get_handle() on _OST prior to executing the method. >> > > > This will ensure that this method only gets run if it is present >> > > under >> > > > the device in question. Coupled with what is already outlined in #1 >> > > > above, now _OST gets executed only when it is defined under the >> > > device object. >> > > > Example case in the existing code, please see >> > > acpi_processor_ppc_ost() >> > > > implementation. >> > > >> > > Yes, I did look at acpi_processor_ppc_ost() when I implemented the >> > > function. I believe calling acpi_get_handle() is redundant since >> > > acpi_ns_get_node() is called within acpi_evaluate_object() as well. >> > > acpi_evaluate_object() simply returns with AE_NOT_FOUND when _OST >> > > method does not exist. >> > > >> > >> > This is correct. If _OST does not exist, AE_NOT_FOUND will be returned >from evaluate_object. >> >> Yes that is correct from the ACPI Spec and implementation point of view. >> My thinking is that a call to acpi_get_handle() might not penalize the >> OS as much as acpi_evaluate_object() would on systems that don't >> actually implement _OST. In other words, acpi_get_handle() might not go >> as deep as acpi_evaluate_object() would go into the ACPI layer, hence >> might be a safer measure on platforms that don't actually implement this >> optional method under all devices included in this patch set. >> > >I do not think we need to worry about it. The code difference is not >that much, and this _OST path is limited to ACPI hotplug operations, >which are infrequent events. Automatic workload balancing can make >frequent use of the operations, but is not frequent enough to make any >difference here. I think simpler code works fine. > >Thanks, >-Toshi -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
