How to default set a parameter value to all then hide the parameter from users in SSRS or would it be done in the SQL?

I am having some trouble backing out a parameter that was initially requested for a report. I keep breaking something so I thought since the parameter is in there and there is an SP list of values that the user will always need all of them....isn't there a simpler way to just default the values to "select all" then hide the parameter from the user so that they don't ever see what is happening in the background. Does anyone have a simple way to do this? Is this a query in SQL or setting in SSRS or both