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Re: [PATCH 2/8] pc-bios: s390x: Get rid of magic offsets into the lowcor


From: Janosch Frank
Subject: Re: [PATCH 2/8] pc-bios: s390x: Get rid of magic offsets into the lowcore
Date: Fri, 27 Mar 2020 11:33:56 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.2.2

On 3/27/20 11:25 AM, David Hildenbrand wrote:
> On 24.03.20 16:08, Janosch Frank wrote:
>> If we have a lowcore struct that has members for offsets that we want
>> to touch, why not use it?
>>
>> Signed-off-by: Janosch Frank <address@hidden>
>> ---
>>  pc-bios/s390-ccw/cio.h  | 17 +++++++++++------
>>  pc-bios/s390-ccw/main.c |  8 +++-----
>>  2 files changed, 14 insertions(+), 11 deletions(-)
>>
>> diff --git a/pc-bios/s390-ccw/cio.h b/pc-bios/s390-ccw/cio.h
>> index aaa432deddb9242e..9ad794a789c47df2 100644
>> --- a/pc-bios/s390-ccw/cio.h
>> +++ b/pc-bios/s390-ccw/cio.h
>> @@ -122,12 +122,17 @@ typedef struct schib {
>>  } __attribute__ ((packed, aligned(4))) Schib;
>>  
>>  typedef struct subchannel_id {
>> -        __u32 cssid:8;
>> -        __u32:4;
>> -        __u32 m:1;
>> -        __u32 ssid:2;
>> -        __u32 one:1;
>> -        __u32 sch_no:16;
>> +    union {
>> +        struct {
>> +            __u16 cssid:8;
>> +        __u16:4;
> 
> Broken indentation. Also, do we want to give that strange-looking
> "__u32:4" a name ("reserved").

Fixed indentation and renamed.

> 
>> +            __u16 m:1;
>> +            __u16 ssid:2;
>> +            __u16 one:1;
>> +        };
>> +        __u16 sch_id;
>> +    };
>> +        __u16 sch_no;
>>  } __attribute__ ((packed, aligned(4))) SubChannelId;
>>  
>>  struct chsc_header {
>> diff --git a/pc-bios/s390-ccw/main.c b/pc-bios/s390-ccw/main.c
>> index 4e65b411e1d890ba..8b912454c940a390 100644
>> --- a/pc-bios/s390-ccw/main.c
>> +++ b/pc-bios/s390-ccw/main.c
>> @@ -36,11 +36,9 @@ LowCore *lowcore; /* Yes, this *is* a pointer to address 
>> 0 */
>>   */
>>  void write_subsystem_identification(void)
>>  {
>> -    SubChannelId *schid = (SubChannelId *) 184;
>> -    uint32_t *zeroes = (uint32_t *) 188;
>> -
>> -    *schid = blk_schid;
>> -    *zeroes = 0;
>> +    lowcore->subchannel_id = blk_schid.sch_id;
>> +    lowcore->subchannel_nr = blk_schid.sch_no;
>> +    lowcore->io_int_parm = 0;
>>  }
>>  
>>  void write_iplb_location(void)
>>
> 
> Looks sane to me.
> 


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