On 07/01/2016 04:01 PM, Rafael J. Wysocki wrote: > On Fri, Jul 1, 2016 at 11:55 PM, Al Stone <ahs3@xxxxxxxxxx> wrote: >> On 07/01/2016 03:46 PM, Rafael J. Wysocki wrote: >>> On Fri, Jul 1, 2016 at 11:41 PM, Al Stone <ahs3@xxxxxxxxxx> wrote: >>>> On 07/01/2016 03:32 PM, Rafael J. Wysocki wrote: >>>>> On Fri, Jul 1, 2016 at 11:21 PM, Al Stone <ahs3@xxxxxxxxxx> wrote: >>>>>> Without this patch, the acpi_parse_entries_array() function will return >>>>>> the very first time there is any error found in either the array of >>>>>> callback functions or if one of the callbacks returns an non-zero value. >>>>>> However, the array of callbacks could still have valid entries further >>>>>> on in the array, or the callbacks may be able to process subsequent >>>>>> subtables without error. The change here makes the function consistent >>>>>> with its description so that it will properly return the sum of all >>>>>> matching entries for all proc handlers, instead of stopping abruptly >>>>>> as it does today. >>>>> >>>>> I'm not sure I follow. >>>>> >>>>> You seem to be saying that the function should process all of the >>>>> subtables etc even though errors have been found for some of them, but >>>>> it still will return an error in the end if there are any errors. How >>>>> exactly does it help to continue processing in case of an error, then? >>>> >>>> The use case I have in mind is to simply count all of the subtables of >>>> a certain type. If for some reason, the callback -- or any other callback >>>> -- fails, the traversal of all the subtables stops immediately. So, I >>>> could have two callbacks, and if the first one fails on the first subtable >>>> of its type, traversal stops. The count for the second callback will be >>>> zero which may or may not be correct. >>> >>> It will be zero, because the callback has not been invoked at all. >>> Why is this incorrect? >>> >> >> Because there could be additional subtables after the one causing a failure >> that the second callback could have counted; e.g., if the failure is on the >> first subtable of 20 in the MADT, the following 19 would be ignored, even if >> they were all the right subtype for the second callback. > > Let me rephrase: Is there any practical value of invoking any more > callbacks if one of them has failed? If so, what is it? > > You are changing semantics from "abort on the first failure" to > "process everything and count errors". That's quite a bit different > and I'm trying to understand why the latter is better. > Agreed, it is a shift in semantics. The practical value to me is being able to use acpi_parse_entries_array() to solve a broader range of problems. The situation I have is that I need to count three different subtable types in the MADT. I could call acpi_table_parse_madt() three different times, or I could call acpi_parse_entries_array() once -- it seemed to me the second makes for cleaner code and will be slightly more efficient (one map/unmap of the table, vs three), but that only works if all of the subtables are traversed. -- ciao, al ----------------------------------- Al Stone Software Engineer Red Hat, Inc. ahs3@xxxxxxxxxx ----------------------------------- -- 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
