2016-11-10 22:35 GMT+09:00 Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>: > On Thu, Nov 10, 2016 at 10:24:21PM +0900, Masahiro Yamada wrote: >> >> sdhci_alloc_host() returns an error pointer when it fails. >> but mmc_alloc_host() cannot. >> >> This series allow to propagate a proper error code >> when host-allocation fails. > > Why? What can we really do about the error except give up? Why does > having a explicit error value make any difference to the caller, they > can't do anything different, right? The error code is shown in the console, like probe of 5a000000.sdhc failed with error -12 The proper error code will give a clue why the driver failed to probe. > I suggest just leaving it as-is, it's simple, and you don't have to mess > with PTR_ERR() anywhere. Why? Most of driver just give up probing for any error, but we still do ERR_PTR()/PTR_ERR() here and there. I think this patch is the same pattern. If a function returns NULL on failure, we need to think about "what is the most common failure case". Currently, MMC drivers assume -ENOMEM is the best fit for mmc_alloc_host(), but the assumption is fragile. Already, mmc_alloc_host() calls a function that returns not only -ENOMEM, but also -ENOSPC. In the future, some other failure cases might be added to mmc_alloc_host(). Once we decide the API returns an error pointer, drivers just propagate the return value from the API. This is much more stable implementation. -- Best Regards Masahiro Yamada -- To unsubscribe from this list: send the line "unsubscribe linux-mmc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
