On 02/28/2017 07:54 PM, Mark Brown wrote: > On Tue, Feb 28, 2017 at 10:24:17AM -0800, Dmitry Torokhov wrote: >> On Tue, Feb 28, 2017 at 09:16:50AM +0000, Mark Brown wrote: >>> On Mon, Feb 27, 2017 at 08:18:56PM -0800, Dmitry Torokhov wrote: >>>> Lists of spi_board_info entries registered with spi_register_board_info() >>>> can be quite long; instead of forcing memory allocator find contagious > >>> Do you have numbers on that? > >> Hm, so the largest array seems to be in >> arch/blackfin/mach-bf537/boards/stamp.c at max of 43 entries. The new >> board info is ether 60 or 72 bytes, so we get 2 or 3K table. Not above >> page, but still could be packed I think. > > Oh wow, that's impressively large. Still not sure the optimization is > particularly worth it though, it's small change in the grand scheme of > things. OTOH it's a small change.
The Blackfin machine files shouldn't be used as valid example. While in theory it is possible to build a kernel with that many entries nobody is ever going to do that. What the Blackfin machine files do is basically a poor man's overlays from the days before overlays existed. Most of the entries in the table use the same chip-select pins, it wouldn't be possible to use use a setup where more than two or three of the entries is enabled at the same time.
