Regular expression for "key = value" pairs

[Ciccio]

Hi all,
suppose I have:

s='a=b, c=d'

and I want to extract sub-strings a,b,c and d from s (and in general 
from any longer list of such comma separated pairs).
Some failed attempts:

In [12]: re.findall(r'(.+)=(.+)', s)
Out[12]: [('a=b, c', 'd')]

In [13]: re.findall(r'(.+?)=(.+)', s)
Out[13]: [('a', 'b, c=d')]

In [14]: re.findall(r'(.+)=(.+)*', s)
Out[14]: [('a=b, c', 'd')]

In [15]: re.findall(r'(.+)=(.+),', s)
Out[15]: [('a', 'b')]

In [16]: re.findall(r'(.+)=(.+),?', s)
Out[16]: [('a=b, c', 'd')]

Thanks for your help,
francesco.