On 11/7/20 11:16 AM, John Hubbard wrote: > On 11/7/20 11:05 AM, Song Bao Hua (Barry Song) wrote: >>> -----Original Message----- >>> From: John Hubbard [mailto:jhubbard@xxxxxxxxxx] > ... >>>> config GUP_BENCHMARK >>>> bool "Enable infrastructure for get_user_pages() and related calls >>> benchmarking" >>>> + depends on DEBUG_FS >>> >>> >>> I think "select DEBUG_FS" is better here. "depends on" has the obnoxious >>> behavior of hiding the choice from you, if the dependencies aren't already met. >>> Whereas what the developer *really* wants is a no-nonsense activation of the >>> choice: "enable GUP_BENCHMARK and the debug fs that it requires". >>> >> >> To some extent, I agree with you. But I still think here it is better to use "depends on". >> According to >> https://www.kernel.org/doc/Documentation/kbuild/kconfig-language.txt >> >> select should be used with care. select will force >> a symbol to a value without visiting the dependencies. >> By abusing select you are able to select a symbol FOO even >> if FOO depends on BAR that is not set. >> In general use select only for non-visible symbols >> (no prompts anywhere) and for symbols with no dependencies. >> That will limit the usefulness but on the other hand avoid >> the illegal configurations all over. >> >> On the other hand, in kernel there are 78 "depends on DEBUG_FS" and >> only 14 "select DEBUG_FS". >> > > You're not looking at the best statistics. Go look at what *already* selects > DEBUG_FS, and you'll find about 50 items. Sorry, I'm not following you. I see the same 14 "select DEBUG_FS" as Barry. In general we don't want any one large "feature" (or subsystem) to be enabled by one driver. If someone has gone to the trouble to disable DEBUG_FS (or whatever), then a different Kconfig symbol shouldn't undo that. -- ~Randy
