From: "Luis R. Rodriguez" mcgrof@do-not-panic.com
Commit 3cf2667 as of next-20130301 extended the struct fb_info with a skip_vt_switch to allow drivers to skip the VT switch at suspend/resume time. For older kernels we can skip this as all this switch does is call pm_vt_switch_required() with true or false depending on this new flag and later pm_vt_switch_unregister() would not have been made.
compat-drivers was backporting this using #ifdef's but by integrating a static inline we'd reduce the number of lines to backport to just 1 line replacement. This would be something like:
- info->skip_vt_switch = true; + fb_enable_skip_vt_switch(info);
For kernels >= 3.10 we'd set the attribute as we do upstream, for older kernels this would be a no-op.
If this static inline would have been added upstream it would have meant this collateral evolution would require just adding a no-op static inline to backport, and no changes as the above example hunk for every driver that requires the change.
If this static inline ends up upstream *now* it means we do *not* require the type of hunk above for every driver that requires the change.
All the code would be left intact !
This is a linux-next 'data structure element collateral evolution'.
Cc: cocci@systeme.lip6.fr Cc: backports@vger.kernel.org Cc: linux-kernel@vger.kernel.org Cc: Julia Lawall julia.lawall@lip6.fr Cc: Rodrigo Vivi rodrigo.vivi@gmail.com Cc: Daniel Vetter daniel.vetter@ffwll.ch Cc: Jesse Barnes jbarnes@virtuousgeek.org Cc: Rafael J. Wysocki rafael.j.wysocki@intel.com Signed-off-by: Luis R. Rodriguez mcgrof@do-not-panic.com --- include/linux/compat-3.10.h | 41 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 41 insertions(+)
diff --git a/include/linux/compat-3.10.h b/include/linux/compat-3.10.h index 69ddc11..9abfc4b 100644 --- a/include/linux/compat-3.10.h +++ b/include/linux/compat-3.10.h @@ -7,6 +7,7 @@
#include <linux/scatterlist.h> #include <linux/mm.h> +#include <linux/fb.h>
#define sg_page_iter_page LINUX_BACKPORT(sg_page_iter_page) /** @@ -29,6 +30,46 @@ static inline dma_addr_t sg_page_iter_dma_address(struct sg_page_iter *piter) return sg_dma_address(piter->sg) + (piter->sg_pgoffset << PAGE_SHIFT); }
+/* + * This is a linux-next data structure element collateral evolution, + * we use a wrapper to avoid #ifdef hell to backport it. This allows + * us to use a simple fb_info_skip_vt_switch() replacement for when + * the new data structure element is used. If coccinelle SmPL grammar + * could be used to express the transformation for us on compat-drivers + * it means we'd need to express it only once. If the structure element + * collateral evolution were to be used *at development* time and we'd + * have a way to express the inverse through SmPL we'd be able to + * backport this collateral evolution automatically for any new driver + * that used it. We'd use coccinelle to look for it and do the + * transformations for us based on the original commit (maybe SmPL + * would be listed on the commit log. + * + * We may need the LINUX_BACKPORT() call that adds the backport_ + * prefix for older kernels than 3.10 if distros decide to + * add this same static inline themselves (although unlikely). + */ +#define fb_enable_skip_vt_switch LINUX_BACKPORT(fb_enable_skip_vt_switch) +static inline void fb_enable_skip_vt_switch(struct fb_info *info) +{ +} + +#else /* kernel is >= 3.10 */ +/* + * We'd delete this upstream ever got this, we use our + * backport_ prefix with LINUX_BACKPORT() so that if this + * does get upstream we would not have to add another ifdef + * here for the kernels in between v3.10.. up to the point + * the routine would have gotten added, we'd just delete this + * #else condition completely. If we didn't have this and + * say 3.12 added the static inline upstream, we'd have a + * clash on the backport for 3.12 as the routine would + * already be defined *but* we'd need it for 3.11. + */ +#define fb_enable_skip_vt_switch LINUX_BACKPORT(fb_enable_skip_vt_switch) +static inline void fb_enable_skip_vt_switch(struct fb_info *info) +{ + info->skip_vt_switch = true; +} #endif /* (LINUX_VERSION_CODE < KERNEL_VERSION(3,10,0)) */
#endif /* LINUX_3_10_COMPAT_H */