kernel - is it harmful to use "volatile" in C? -

kernel - is it harmful to use "volatile" in C? -

i new sparse. , during running sparse seeing warning:

warning: wrong type in argument 2 (different address spaces)

expected void volatile [noderef] <asn:2>*addr got void *

basically, happening because of following:

struct context{ void __iomem *base; }; readl(const volatile void __iomem* add){ .... .... } function: foo(){ struct context *var; readl(var->base); //---> here got above mentioned warning }

to prepare did following:

struct context{ - void __iomem *base; + volatile void __iomem *base; };

and warning removed.

my question: - harmful utilize "volatile" in such case. , if yes why? - think should not create fellow member of struct "volatile". but, how can rid off csparse warning.

as per documentation given @ https://www.kernel.org/doc/documentation/volatile-considered-harmful.txt @ http://lwn.net/articles/233482/. should avoid utilize of volatile.

no, it's not harmful. no thought why should or be, harmful what?

if code you're calling expects volatile pointer, it's wrong pass non-volatile one, since code in calling context might not adapted requirements of volatile value in case.

c kernel volatile sparse-matrix