Hi Andy, >-----Original Message----- >From: Andy Shevchenko [mailto:andriy.shevchenko@xxxxxxxxxxxxxxx] >Sent: 16 June 2020 13:41 >To: Shiju Jose <shiju.jose@xxxxxxxxxx> >Cc: linux-acpi@xxxxxxxxxxxxxxx; linux-pci@xxxxxxxxxxxxxxx; linux- >kernel@xxxxxxxxxxxxxxx; rjw@xxxxxxxxxxxxx; bp@xxxxxxxxx; >james.morse@xxxxxxx; lenb@xxxxxxxxxx; tony.luck@xxxxxxxxx; >dan.carpenter@xxxxxxxxxx; zhangliguang@xxxxxxxxxxxxxxxxx; Wangkefeng >(OS Kernel Lab) <wangkefeng.wang@xxxxxxxxxx>; jroedel@xxxxxxx; >yangyicong <yangyicong@xxxxxxxxxx>; Jonathan Cameron ><jonathan.cameron@xxxxxxxxxx>; tanxiaofei <tanxiaofei@xxxxxxxxxx>; >Linuxarm <linuxarm@xxxxxxxxxx> >Subject: Re: [PATCH v9 2/2] PCI: hip: Add handling of HiSilicon HIP PCIe >controller errors > >On Tue, Jun 16, 2020 at 11:55:46AM +0000, Shiju Jose wrote: >> >From: linux-acpi-owner@xxxxxxxxxxxxxxx [mailto:linux-acpi- >> >owner@xxxxxxxxxxxxxxx] On Behalf Of Andy Shevchenko On Tue, Jun 16, >> >2020 at 09:12:56AM +0000, Shiju Jose wrote: >> >> >From: Andy Shevchenko [mailto:andriy.shevchenko@xxxxxxxxxxxxxxx] >> >> >On Mon, Jun 15, 2020 at 11:15:52AM +0100, Shiju Jose wrote: > >... > >> >> >> +#define HISI_PCIE_CORE_PORT_ID(v) (((v) % 8) << 1) >> >> > >> >> >% -> & ? >> >> (((v) % 8) << 1) is correct. We can make bit operation instead. >> > >> >y % x is usually being used when we consume y / x or in cases when y >> >is advanced and we need to keep it under some threshold. >> > >> >Here it's not obvious to me, and usual pattern is to use bitwise >operations. >> > >> >In any case some clarification is needed. >> We want (v % 8) * 2 here to get the core port id, a numerical value but not >a bit mask. >> Maybe you want us to use ((v) & 7) << 1? >> please point it out if I understand wrong. > >I understand the result, I do not understand the properties of v. >So, looks like >a) (v & 7) << 1 // take 3 LSBs from v and shift right to get port id pair (looks >like) >b) (v % 8) * 2 // get next free port or circle over 0 if no free pair found > >Add some comment explaining what's going on. Sure. > >... > >> >> >> + switch (id) { >> >> >> + case HISI_PCIE_SUB_MODULE_ID_AP: return "AP Layer"; >> >> >> + case HISI_PCIE_SUB_MODULE_ID_TL: return "TL Layer"; >> >> >> + case HISI_PCIE_SUB_MODULE_ID_MAC: return "MAC Layer"; >> >> >> + case HISI_PCIE_SUB_MODULE_ID_DL: return "DL Layer"; >> >> >> + case HISI_PCIE_SUB_MODULE_ID_SDI: return "SDI Layer"; >> >> >> + } >> >> > >> >> >match_string() ? >> >> >> >> match_string() does not work here because we need sub module id -> >> >> string conversion. >> > >> >Why? Are you using non-sequential (a.k.a. sparse) values? >> These are the sequential values. >> I mean in this case we do not have the third parameter to the >> match_string(), string to match with the strings in the array, we just >> have the value for the sub module id. >> Can you suggest some example of match_string() for the similar case? > >Ah, I realize, this is the opposite, but still perhaps better to have like this: > >static const char * const foo[] = { > "AB", > "CD", >}; > >const char *bar(int id) >{ > if (id >= ARRAY_SIZE(foo)) > return "unknown"; // whatever > return foo[id]; >} Sure. > >-- >With Best Regards, >Andy Shevchenko > Thanks, Shiju
