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Date: Wed, 14 Aug 2013 17:00:53 +0930 From: Rusty Russell <rusty@...tcorp.com.au> To: Steven Rostedt <rostedt@...dmis.org>, linux-kernel@...r.kernel.org Cc: Andrew Morton <akpm@...ux-foundation.org> Subject: Re: [PATCH 1/3] [PATCH 1/3] module: Add flag to allow mod params to have no arguments Steven Rostedt <rostedt@...dmis.org> writes: > Currently the params.c code allows only two "set" functions to have > no arguments. If a parameter does not have an argument, then it > looks at the set function and tests if it is either param_set_bool() > or param_set_bint(). If it is not one of these functions, then it > fails the loading of the module. > > But there may be module parameters that have different set functions > and still allow no arguments. But unless each of these cases adds > their function to the if statement, it wont be allowed to have no > arguments. This method gets rather messing and does not scale. > > Instead, introduce a flags field to the kernel_param_ops, where if > the flag KERNEL_PARAM_FL_NOARG is set, the parameter will not fail > if it does not contain an argument. It will be expected that the > corresponding set function can handle a NULL pointer as "val". Good idea. This hack was introduced because people wrote their own param parsers which didn't expect NULL, leading to oopsen. A flag is a better solution. Applied all three. Thanks, Rusty. > > Signed-off-by: Steven Rostedt <rostedt@...dmis.org> > --- > include/linux/moduleparam.h | 13 ++++++++++++- > kernel/params.c | 6 ++++-- > 2 files changed, 16 insertions(+), 3 deletions(-) > > diff --git a/include/linux/moduleparam.h b/include/linux/moduleparam.h > index 27d9da3..c3eb102 100644 > --- a/include/linux/moduleparam.h > +++ b/include/linux/moduleparam.h > @@ -36,7 +36,18 @@ static const char __UNIQUE_ID(name)[] \ > > struct kernel_param; > > +/* > + * Flags available for kernel_param_ops > + * > + * NOARG - the parameter allows for no argument (foo instead of foo=1) > + */ > +enum { > + KERNEL_PARAM_FL_NOARG = (1 << 0) > +}; > + > struct kernel_param_ops { > + /* How the ops should behave */ > + unsigned int flags; > /* Returns 0, or -errno. arg is in kp->arg. */ > int (*set)(const char *val, const struct kernel_param *kp); > /* Returns length written or -errno. Buffer is 4k (ie. be short!) */ > @@ -187,7 +198,7 @@ struct kparam_array > /* Obsolete - use module_param_cb() */ > #define module_param_call(name, set, get, arg, perm) \ > static struct kernel_param_ops __param_ops_##name = \ > - { (void *)set, (void *)get }; \ > + { 0, (void *)set, (void *)get }; \ > __module_param_call(MODULE_PARAM_PREFIX, \ > name, &__param_ops_##name, arg, \ > (perm) + sizeof(__check_old_set_param(set))*0, -1) > diff --git a/kernel/params.c b/kernel/params.c > index 440e65d..27a0af9 100644 > --- a/kernel/params.c > +++ b/kernel/params.c > @@ -103,8 +103,8 @@ static int parse_one(char *param, > || params[i].level > max_level) > return 0; > /* No one handled NULL, so do it here. */ > - if (!val && params[i].ops->set != param_set_bool > - && params[i].ops->set != param_set_bint) > + if (!val && > + !(params[i].ops->flags & KERNEL_PARAM_FL_NOARG)) > return -EINVAL; > pr_debug("handling %s with %p\n", param, > params[i].ops->set); > @@ -320,6 +320,7 @@ int param_get_bool(char *buffer, const struct kernel_param *kp) > EXPORT_SYMBOL(param_get_bool); > > struct kernel_param_ops param_ops_bool = { > + .flags = KERNEL_PARAM_FL_NOARG, > .set = param_set_bool, > .get = param_get_bool, > }; > @@ -370,6 +371,7 @@ int param_set_bint(const char *val, const struct kernel_param *kp) > EXPORT_SYMBOL(param_set_bint); > > struct kernel_param_ops param_ops_bint = { > + .flags = KERNEL_PARAM_FL_NOARG, > .set = param_set_bint, > .get = param_get_int, > }; > -- > 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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