#8922 NORM Not Tri: EC battery queries should indicate "missing" status

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#8922: EC battery queries should indicate "missing" status
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   Reporter:  pgf           |       Owner:  pgf                              
       Type:  enhancement   |      Status:  new                              
   Priority:  normal        |   Milestone:  Not Triaged                      
  Component:  not assigned  |     Version:  Development build as of this date
 Resolution:                |    Keywords:                                   
Next_action:  code          |    Verified:  0                                
  Blockedby:                |    Blocking:                                   
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Comment(by pgf):

 quoting from the devel mailing list

 {{{
 Date:    Sat, 01 Nov 2008 18:26:16 EDT
 To:      Paul Fox
 cc:      richard, dilinger, devel
 From:    Andres Salomon
 Subject: Re: ec battery commands


 On Sat, 01 Nov 2008 16:39:49 -0400
 Paul Fox wrote:

 > hi dilinger -- one of the tasks on the EC punchlist is this one:
 >
 > "Make battery commands return 0xff (or some other invalid value)
 > if the battery is not present.  This will be an error indication
 > for the kernel."
 >
 > can you point me at the kernel code that cares about this, and, in
 > particular if you can remember, for which commands it's most important
 > to have this behavior changed?  i'd like to be sure i understand
 > the req'ts before implementing anything.
 >

 Certainly; the specific code is drivers/power/olpc_battery.c.  The code
 that
 is acutally querying the battery status is olpc_bat_get_property().  Due
 to the current limitations of the API, we cannot simply fetch EC_BAT_ACR;
 every value is valid, and (aiui) the EC will simply return the last known
 value.  This is undesirable if there's no battery present, so we currently
 first check EC_BAT_STATUS (for PRESENT), and then run the necessary EC
 command.  This means that each query ends up running 2 EC commands.  It
 would be nice to cut that down to 1.

 Along those lines, it would be nice if there was an error value that we
 could check for if the EC thinks that there is no battery present, and
 we run some random command that is querying for battery info.  Richard
 and I discussed this a bunch a long time ago, but it was in person and
 my memory is fuzzy..  I don't remember if we came up w/ a value that
 would work across all EC battery commands.  It would kind of suck if
 we had to have different error codes for different commands, but that
 would still be better than our current behavior.
 _______________________________________________
 Devel mailing list
 Devel at lists.laptop.org

 }}}

-- 
Ticket URL: <http://dev.laptop.org/ticket/8922#comment:1>
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