> This is an overwhelmingly long name, please use the same name as
> the function that uses this feature, i.e. just 'grep-read-files'.
> Then when someone reading dired.el will find a line
> 
>   (put 'dired-mode 'grep-read-files 'dired-grep-read-files)
> 
> it will be clear for them the purpose of this feature.

Good point, I've changed it to grep-read-files.

> Please place this change in dired.el after the definition of
> 'dired-file-name-at-point' that you can use in your dired function
> instead of (run-hook-with-args-until-success 
> 'file-name-at-point-functions)

Thanks, also done this.

> If you want you could also add as a 4th option additionally
> (run-hook-with-args-until-success 'file-name-at-point-functions)
> to automatically support modes other than dired, i.e. other modes
> that set file-name-at-point-functions.

Sounds like a sensible default, added this as well.

Patch attached.