RTDM read/write callback with parameters

Martin Haag haag at aim-online.com
Wed Sep 23 10:00:54 CEST 2020

Am 22.09.2020 um 17:18 schrieb Jan Kiszka:
> On 21.09.20 15:49, Martin Haag via Xenomai wrote:
>> Dear list members,
>> I am porting a Linux PCI character device driver to Xenomai 2.6.5.
>> I can not find a RTDM expression for the "parameters" argument of the
>> struct file_operations read callback.
>> struct file_operations:
>> ssize_t aim_read(struct file* file, char __user *parameters, size_t
>> parameterSize, loff_t* offset);
>> struct rtdm_operations:
>> ssize_t aim_rtdm_read(struct rtdm_dev_context *context, rtdm_user_info_t
>> *user_info, void *buf, size_t nbyte)
> buf would map to parameter in the kernel interface, and there is no 
> equivalent of offset.
> HTH,
> Jan
Thanks for the confirmation. This is what I found out when I tried to 
use "buf" as input yesterday. I guess what confused me was the "buf" 
parameter being documented as "[out]" for the read callback.

> typedef ssize_t(* rtdm_read_handler_t)(struct rtdm_dev_context 
> *context, rtdm_user_info_t *user_info, void *buf, size_t nbyte)
> Read handler.
> Parameters
> [in]    context    Context structure associated with opened device 
> instance
> [in]    user_info    Opaque pointer to information about user mode 
> caller, NULL if kernel mode call
> [out]    buf    Input buffer as passed by the user
> [in]    nbyte    Number of bytes the user requests to read

Best Regards,

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