| Message ID | 1454756672-12790-2-git-send-email-zhang.chunyan@linaro.org |
|---|---|
| State | New |
| Headers | show |
On 12 February 2016 at 08:18, Alexander Shishkin <alexander.shishkin@linux.intel.com> wrote: > Chunyan Zhang <zhang.chunyan@linaro.org> writes: > >> There is already an interface of set_options, but no get_options yet. >> Before setting any options, one would may want to see the current >> status of that option by means of get_options interface. This >> interface has been used in CoreSight STM driver. > > I'm not sure I understand the reasoning behind this. If a userspace > program opens a communication channel and wants to configure certain > features on it, why does its choice depend on what has been configured > for this channel previously? It can be anything at all. Most likely, > it's either unconfigured or configured to its default values, but why > does this matter for a new writer? A client may wish to change the settings (invariant/guaranteed) it has on a specific channel - it may even want to so do multiple times. The idea behind introducing a get_options() was to probe the specific settings of a channel before going a head with a new configuration. In hindsight it may not be needed as a client should simply go ahead and push down the configuration it wants. > > Regards, > -- > Alex
diff --git a/drivers/hwtracing/stm/core.c b/drivers/hwtracing/stm/core.c index b6445d9..854a16d 100644 --- a/drivers/hwtracing/stm/core.c +++ b/drivers/hwtracing/stm/core.c @@ -571,6 +571,18 @@ stm_char_ioctl(struct file *file, unsigned int cmd, unsigned long arg) options); break; + + case STP_GET_OPTIONS: + if (stm_data->get_options) + err = stm_data->get_options(stm_data, + stmf->output.master, + stmf->output.channel, + stmf->output.nr_chans, + &options); + + if (copy_to_user((void __user *)arg, &options, sizeof(u64))) + return -EFAULT; + default: break; } diff --git a/include/linux/stm.h b/include/linux/stm.h index 9d0083d..f351d62 100644 --- a/include/linux/stm.h +++ b/include/linux/stm.h @@ -88,6 +88,9 @@ struct stm_data { long (*set_options)(struct stm_data *, unsigned int, unsigned int, unsigned int, unsigned long); + long (*get_options)(struct stm_data *, unsigned int, + unsigned int, unsigned int, + u64 *); }; int stm_register_device(struct device *parent, struct stm_data *stm_data, diff --git a/include/uapi/linux/stm.h b/include/uapi/linux/stm.h index 626a8d3..0dab16e 100644 --- a/include/uapi/linux/stm.h +++ b/include/uapi/linux/stm.h @@ -46,5 +46,6 @@ struct stp_policy_id { #define STP_POLICY_ID_SET _IOWR('%', 0, struct stp_policy_id) #define STP_POLICY_ID_GET _IOR('%', 1, struct stp_policy_id) #define STP_SET_OPTIONS _IOW('%', 2, __u64) +#define STP_GET_OPTIONS _IOR('%', 3, __u64) #endif /* _UAPI_LINUX_STM_H */
There is already an interface of set_options, but no get_options yet. Before setting any options, one would may want to see the current status of that option by means of get_options interface. This interface has been used in CoreSight STM driver. Signed-off-by: Chunyan Zhang <zhang.chunyan@linaro.org> --- drivers/hwtracing/stm/core.c | 12 ++++++++++++ include/linux/stm.h | 3 +++ include/uapi/linux/stm.h | 1 + 3 files changed, 16 insertions(+) -- 1.9.1